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Gravity Force Lab: Basics is an interactive sim. It changes as you play with it. It has a Play Area and a Control Area.

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Easy Rube Goldberg Ideas: Easy Rube Goldberg Machine for Kids

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Sesame Street: Building Rube Goldberg Machines Compilation!

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Giant Kids' RUBE GOLDBERG Machine! | Kids Invent Stuff

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Fun Magnet Facts for Kids

Check out our fun magnet facts for kids and enjoy learning some truly magnetic information about the world of magnetism.

Find out what a magnet is, how magnetic fields work, which metals are magnetic and which aren't, how the Earth's core relates to magnetism and much more. Read on and have fun learning about magnets!

Magnets are objects that produce an area of magnetic force called a magnetic field.

Magnetic fields by themselves are invisible to the human eye.

Iron filings can be used to show magnetic fields created by magnets (such as in the picture to the right).

Magnets only attract certain types of metals, other materials such as glass, plastic and wood aren't attracted.

Metals such as iron, nickel and cobalt are attracted to magnets.

Most metals however are not attracted to magnets, these include copper, silver, gold, magnesium, platinum, aluminium and more. They may however magnetize a small amount while placed in a magnetic field.

Magnetism can attract magnetic objects or push them away.

Magnets have a magnetic north pole and a magnetic south pole. If the same pole of two magnets are placed near each other they will push away (repel), while if different poles are placed near each other they will pull together (attract).

Magnetic objects must be inside the magnetic field to respond, which is why you may have to move a magnet closer for it to have an effect.

The Earth's core is believed to be a mix (alloy) of iron and nickel, giving the Earth its own magnetic field.

The Earth's magnetic field is responsible for deflecting the solar wind, charged particles that come from the Sun.

Magnetic compasses use the Earth's magnetic field to help navigate in north, south, east and west directions.

Electromagnets are created by an electric current running through a surrounding coil. They have many uses including the generation of electricity in hydroelectric dams.

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Fun Magnet Facts for Kids - Magnetic Information about Magnetism

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Fun Magnet Facts for Kids Check out our fun magnet facts for kids and enjoy learning some truly magnetic information about the world of magnetism. Find out what a magnet is, how magnetic fields work, which metals are magnetic and which aren't, how the Earth's core relates to magnetism and much more.

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Have you played with magnets before? Well we're sure you must have, as most of us have at some point.

Now what you will know is that all magnets can pull things towards themselves no matter what the shape of the magnet is. That is what magnetism is.

They can't pull things like paper, glass or cloth, only things that are made of iron or that contain iron, so if you try and attach a magnet to something plastic, it's just not going to work.

Magnets are usually made of metal iron or another material with lots of iron in it, like steel.

There are different types of magnets and some have super fancy names like Air-core magnets, Electromagnets and Permanent magnets.

The ones we usually see are mostly man-made by using electricity.

There are also naturally magnetic rocks called lodestone found on the Earth's surface and in the past people made them magnetic by rubbing iron on the rock surface.

This made the electrons inside them pull in the same direction.

What is iron?

Iron is made up of tiny particles called atoms and each iron atom is made up of 26 electrons.

Magnets are like a big invisible force that we can't see, just like the wind. But even though we can't actually see the force, we can see what the force does to things around it.

In the olden days people thought magnets were magic because as they would see things move without being touched!

Below is a picture of magnetic field lines, which we can't see with our eyes.

Why are Magnets Important?

Magnets are great fun to play with but they are also seriously important and they are used in so many ways in our world.

They hold notes to the fridge and help close fridge doors.

They are used in microwaves, electric fans, earphones, speakers, in medical equipment, electronics and in nearly all electric machines that use motor engines to make them work.

Wow, who would have thought that they were used in so many things?

How Does Magnetism Work?

Magnets have two ends to them. These are called poles - a North Pole and a South Pole, just the same as on Earth.

The two ends of the magnet may look the same but they don't do the same things.

If you get two 'North Pole' magnet ends - or two 'South Pole' magnet ends - and try putting them together, they will push away from each other.

But if you take a 'North Pole' magnet end and put it near a 'South Pole' magnet end, they will pull towards each other.

Another interesting thing is if you chop a magnet in half, you get two identical magnets and each has a North and a South Pole, so you will never find a magnet with just a South Pole or just a North Pole.

Our Earth is a like a massive magnet with a liquid metal core deep inside it which spins, creating a magnetic field with a North and South Pole.

The field is strongest at the actual poles. The sun is also very magnetic.

Before GPS satellites were invented, the compass was used to tell us what direction we were facing - this would be rather useful if you were stuck in the middle of the ocean.

The magnetic compass was a simple tool with a magnet which balanced, called a needle. The one end was often marked "N," for north, or colored in some way to show that it pointed north.

Because of the earth's magnetic field the magnetic needle was always drawn to the magnetic North Pole. It doesn't point exactly north because true north is at the North Pole.

The needle points to the magnetic North Pole which is about 620 miles (1,000 kilometers) south of true north.

Electricity and magnetism have a strong connection with each other and scientists call this 'electromagnetism'.

Without it we would have no electricity in our homes or electric motors.

The term comes from knowing that a magnet can create an electric current and an electric current produces magnetism.

So, there's everything you need to know about magnetism. We hope it is nice and clear and that you'll be a super kid in all things magnetism when you're asked about it!

Useful Websites
Magnets on BBC Bitesize
Magnetism Quiz

Click to take our magnetism quiz - all answers can be found somewhere on this page!

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Have you played with magnets before? Well we're sure you must have, as most of us have at some point. Now what you will know is that all magnets can pull things towards themselves no matter what the shape of the magnet is. That is what magnetism is.

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Magnets for Kids | Science Lesson for Grades 3-5 | Mini-Clip

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Magnets and Magnetism | Magnets Video for Kids

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There is also a text version of this lab.

These Labs require the most recent version of the Flash plug-in. You can download Flash from the Macromedia web site for free.

If you are having trouble with Flash, please take a look at our Help page.

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There is also a text version of this lab. These Labs require the most recent version of the Flash plug-in. You can download Flash from the Macromedia web site for free. If you are having trouble with Flash, please take a look at our Help page.

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What is Force? | Ready Jet Go! | PBS LearningMedia

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Worst chore ever... or is it actually the best? In this clip from Ready Jet Go!, Jet and his friends do a typical Bortronian chore: riding around the neighborhood on Ka-Flooples! While doing their "chore", Sydney asks Face 9000 what force is.

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Physics4Kids.com! This tutorial introduces the physics of gravity. Other sections include modern physics, heat, electricity, magnetism, and light.

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Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun.

What else does gravity do?

Why do you land on the ground when you jump up instead of floating off into space? Why do things fall down when you throw them or drop them? The answer is gravity: an invisible force that pulls objects toward each other. Earth's gravity is what keeps you on the ground and what makes things fall.

Anything that has mass also has gravity. Objects with more mass have more gravity. Gravity also gets weaker with distance. So, the closer objects are to each other, the stronger their gravitational pull is.

Earth's gravity comes from all its mass. All its mass makes a combined gravitational pull on all the mass in your body. That's what gives you weight. And if you were on a planet with less mass than Earth, you would weigh less than you do here.

You exert the same gravitational force on Earth that it does on you. But because Earth is so much more massive than you, your force doesn't really have an effect on our planet.

Gravity in our universe

Gravity is what holds the planets in orbit around the sun and what keeps the moon in orbit around Earth. The gravitational pull of the moon pulls the seas towards it, causing the ocean tides. Gravity creates stars and planets by pulling together the material from which they are made.

Gravity not only pulls on mass but also on light. Albert Einstein discovered this principle. If you shine a flashlight upwards, the light will grow imperceptibly redder as gravity pulls it. You can't see the change with your eyes, but scientists can measure it.

Black holes pack so much mass into such a small volume that their gravity is strong enough to keep anything, even light, from escaping.

Gravity on Earth

Gravity is very important to us. We could not live on Earth without it. The sun's gravity keeps Earth in orbit around it, keeping us at a comfortable distance to enjoy the sun's light and warmth. It holds down our atmosphere and the air we need to breathe. Gravity is what holds our world together.

However, gravity isn't the same everywhere on Earth. Gravity is slightly stronger over places with more mass underground than over places with less mass. NASA uses two spacecraft to measure these variations in Earth's gravity. These spacecraft are part of the Gravity Recovery and Climate Experiment (GRACE) mission.

GRACE detects tiny changes in gravity over time. These changes have revealed important details about our planet. For example, GRACE monitors changes in sea level and can detect changes in Earth's crust brought on by earthquakes.

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Gravity is the force by which a planet or other body draws objects toward its center.

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Defining Gravity: Crash Course Kids #4.1

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Absorbent - a substance that can soak up a liquid, or to take in energy and retain it.

Absorber - an absorber does not reflect or transmit particles or radiation that hit it. Aluminium foil is an absorber of alpha particles. A dark, dull surface is an absorber of infra-red radiation.

Accuracy - is a term that refers to the properties of a measuring instrument.

Acid - an acid is a chemical that will neutralize a base such as an alkali. There are many different kinds of acid. Lemons are sour because they contain citric acid. Acid in vinegar is called acetic acid. It is a substance that disolves in water to form a solution with a pH below 7. An acid contains hydrogen which can be replaced by a metal to form a salt. When an acid dissolves in water H+(aq) ions are formed. A strong acid completely ionises in water and a weak acid only partly ionises. Common strong acids include hydochloric acid, HCl, sulphuric acid, H2SO4 and nitric acid, HNO3. A common weak acid is ethanoic acid, CH3COOH.

Acid rain - is a kind of pollution. Sulphur and nitrogen oxides are produced from the burning of fossil fuels. When they escape into the atmosphe, they form sulphuric and nitric acids. Thes acids can have effects on our environment, e.g. erode stonework, lower the pH of lakes and rivers killing our wildlife, and cause damage to trees.

Adhesive - made to stick like glue.

Air - is a mixture of gases.

Alkali - is a metal oxide or hydroxide (base) that dissolves in water to form a solution with a pH greater than 7. An alkali is neutralised by an acid to form a salt and water. Common alkalis include sodium hydroxide, NaOH, potassium hydroxide, KOH, calcium hydroxide, Ca(OH)2 and ammonium hydroxide, NH4OH.

Alloy - is a metal made by melting and mixing two or more metals together, e.g. brass is a mixture of copper and zinc and bronze is an alloy of copper and tin.

Amphibians - are animals that live in water and on land. They have smooth, moist skins and lay their eggs in water.

Antennae - a pair of sensory organs found on the heads of insects.

Apparatus - are the things (equipment) needed to carry out an experiment.

Aquatic - belonging to , or living in water.

Atomic - an atom is the smallest particle (unit of matter) of an element which can exist and be part of a chemical reaction (a source of nuclear energy). The tiniest part of a substance. Atomic is the use of atomic bombs or energy.

Bacteria - are very small single-celled organisms with no nucleus.

Balance/Top Pan Balance - is an instrument which is used to measure mass.

Barbule - branches that form from the hollow shaft (Rachis) of a feather. When birds preen (groom) their feathers they spread oils over them which 're-hooks' the barbules.

Battery - a battery consists of a number of electrical cells. These cells are usually connected in series to give a highter voltage than that from a sinlge cell.

Bedrock - solid rock immediatley beneath the surface soil.

Biodegradable - is a material that can rot and decay away quickly after we have used it.

Biologist - to study biology you will need to know the 7 life processes. A memory trick to remember what the life processes are is'MRS GREN'.

M - Movement - the moving parts of an organism

R - Reproduction - Producing offspring

S - Sensitivity - Reacting and responding to the environment

G - Growth - Increasing is size to adulthood

R - Respiration - Turning food into energy

E - Excretion - Getting rid of waste

N - Nutrition - Getting food to stay alive

Birds - are animals that have feather and wings. They lay eggs with hard shells and usually fly.

Bonded - Something that is bound, fastened or joined together.

Braided - interwoven hair and thread, or other fibres and yarns.

Bulb - part of the root of a plant which resembles a ball (e.g. onion).

Bunsen burner - is a gas burner used in a lab during experiments.

Canopy - a hanging cover forming a shelter.

Carnivores- are animals that eat other animals.

Catalyst - is something that alters the speed (speeds up) of a chemical reaction or change without being used up at the end of it or permanently changed itself.

Cells - one of the smallest parts of a plant or animal tissue.

Circuit - is one or more conducting paths between the two electrodes of a cell or battery of cells.

Characteristics - the distinguishing features or quality of something.

Chemicals - are the substances used in chemistry doing experiments..

Chemist - a chemist needs to be able to identify acids and alkalis. Universal Indicator can be used to show the pH of a substance.

Classifying - is to sort things into different groups.

Climate - the weather conditions of an area (e.g. the hot Siberian desert, the coldness of Iceland).

Compound - is a substance that has two or more elements in it.

Concave - describes the shape of a lens or other object where the center is thinner than the outside.

Conclusion - things that can be worked out from doing an experiment (making a decision). To draw to a close, to finish or conclude with an explanation, judgement or opinion based on interpretations.

Condensation - is the change from a gas to a liquid or solid.

Conifers - are relating to or part of trees or shrubs that do not have flowers and their seeds are made in cones.

Consistence - a degree of thickness or smoothness of a substance.

Controlled Variable - the things that you try to keep the same in an experiment or investigation.

Corrosion - is the wearing away of the surface of a metal by chemical reactions with oxygen and water. Rusting is one example of corrosion.

Crystals - a solid with a symmetrical arrangement of faces, usually bright and clear.

Current - is a flow of electric charge. The current is a metallic conductor is due to a flow of negatively charged electrons.

Data - a collection of observations, measurements and/or facts.

Decompose - the breaking down of parts from a whole - to decay or rot, wasting away.

Dense - made up of very closely packed particles.

Dilute - is to make a liquid weaker or thinner by adding more liquid, usually more water.

Dispersion - is the splitting of white light into the seven colors of the visible spectrum - rainbow.

Dissolving - is the process that occurs when a solute is added to a solvent and the solute disappears. The particles of the solute fit between the particles of the solvent. The solute can be recovered by the evaporation process. To mix a solid with a liquid so it becomes a liquid as well. To melt, to become a liquid (ice melting, sugar disolving in hot tea).

Distillation - this is to separate a liquid from other liquids by boiling it and condensing the steam. A substance that has been through an evaporation and condensing process.

Earth - is the planet that we inhabit. In electricity, the term refers to an electrical connection to the Earth.

Ecosystem - is the sum total of all the living organisms and non-living factors in an environment and the way they interact. The relationship between the environment, its animals and its plants.

Eiderdown - Eider is a duck which has very soft feathers, eiderdown is the down (feathers) from this duck.

Element - is a pure substance made of one kind of atom. It cannot be split up into anything simpler without losing its characteristics. A substance that cannot be separated into simpler substances.

Energy - is transfered by heating by; radiation, conduction and convection. The amount of energy transfered is measured in joules.

Environment - the conditions or surroundings in which people and animals live.

Enzymes - is a substance that speeds up a chemical reaction in the body (a biological catalyst). Each enzyme works best at a particular temperature and pH.

Erosion - is the process where rocks are worn away.

Evaluating - to decide if you have done something the best way and seeing what you could improve.

Evaporation - is the process in which a liquid changes to a vapour, due to particles leaving the surface of the liquid. A liquid turns to a gas. Changing from a liquid or a solid into vapours (gas).

Evidence - is anything that gives a reason to believe something.

Expand - is when the size of a substance increases due to being heated. The particles gain energy and move further apart.

Experiment - a test to find something out.

Explosion - is a very rapid reaction accompanied by a large expansion in gases.

Fabric - any material made of fibers or yarn which has been woven or knitted together.

Fair Test - is controlling some of the things used or done in a test so they do not change. An experiment in which only one variable is changed at a time to allow a fair comparison.

Felt - is tightly matted fabric made of wool which has had the fibers worked together under pressure.

Ferns - a plant with strong stems, roots and leaves and do not have seeds.

Fertilize - to provide a plant with pollen to bring about fertilization.

Filaments - are single stands of fiber.

Filter - is to separate solids (that do not dissolve) from liquids.

Fish - are cold-blooded animals that live in water, they have a backbone, scaly skin, tails and fins for swimming and gills for breathing.

Flammable - a substance or material that easily sets on fire.

Flowering Plants- any plant that produces flowers and fruit.

Force - is a push or pull. Force is measured in units called newtons (N).

Formula - is a way of writing scientific information using letters, numbers and signs.

Friction - occurs when two surfaces move over each other. Air resistance and water resistnace are friction forces caused by the movement of something through the air or the water.

Freeze - is when you cool something to a very low temperature and it usually forms ice.

Function - is the special purpose or use of something.

Galaxy - is a group of millions of stars held together by gravity, like the Milky Way.

Gas - is a state of matter in which the particles move rapidly and are very spread out.

Gravity - is the force of attraction between any two bodies. It increases with increasing mass of the bodies and decreases if they are further apart.

Habitat - is a place where an organism lives. It is the natural home of a plant or animal.

Herbivores - are animals that eat only plants.

Humidity - is warm dampness, it is a measure of the amount of water in the air.

Humus - bits of decaying plants and animals found in soil.

Igneous - (of rock) is the matter formed as moulten (entremely hot liquid) rock cools and hardens.

Indicator - is a chemical that can show if a substance is acidic or alkaline by changing color. Color turns red in acid and blue in alkali.

Infiltration - is the passing of a liquid or gas through a substance by means of a filter.

Insoluble - this is when a solid is unable to dissolve into a liquid.

Insulator - halts the passage of electricity, heat or sound through an object or substance.

Invertebrates - are animals without a backbone, such as worms.

Investigating - is to look for clues and try to work out what they mean.

Joule (J) - is the unit for measuring energy or work.

Kaleidoscope - is a tube filled with colored paper, which is lined with mirrors placed at different angles. Turning the tube will create amazing patterns for you to see through a small hole at the end of the tube.

Keratin - is a fibrous protein found in hair and nails.

Kinetic Energy - is the kind of energy in moving things.

Larva, larvae - is an insect that is still in its caterpillar state.

Leaf - is a flat green blade attached to the stem of a plant.

Lichen - is a mutualistic relationship between a fungus and an alga (simple plant). They can be seen as crusty patches on tree trunks and walls.

Liquid - is a state of matter in which the particles are close together but randomly arranged. The particles can move over each other.

Magnetic - applies to any object or material that is repelled or attracted by a magnet. Magnetic materials include iron, steel, cobalt and nickel.

Magnetic field - is an area where a magnetic material experiences a force. Magnetic fields exist around permanent magnets, electromagnets and electric currents.

Magnification - to be magnified. To increase the size of an object to make it bigger than it actually is.

Mammals - are animals that are warm-blooded, usually have fur or hair and feed their young with milk from their mother.

Matter - is the material that something is made up of.

Melting - is when a solid changes to a liquid at the melting point by heating.

Melting Point - is when the temperature at which a solid changes to a liquid.

Measuring Cylinder - is an instrument that measures the volume of a liquid.

Metamorphic - (of rock) is a complete change from its original state caused by heat and pressure.

Method - is an orderly way of doing something.

Methodology - is a scientific study of method. A system of methods used in a particular activity.

Microbes - are very small living things, usually only one cell big. A tiny organism that can only be seen with a microscope. Some microbes can cause disease.

Milky Way - is the spiral galaxy of stars which the Earth is part of.

Minibeasts - are miniature or very small animals such as insects.

Mixture - is two or more substances mixed together without actually joining them so that they can be separated again.

Molecule - is a group of atoms joined together.

Moss - a plant that has weak roots, thin, delicate leaves and do not have seeds.

Moult - is the shedding or casting off of feathers, hair, fur and skin.

Nectar - is the sweet juice of flowers from which bees make their honey.

Neutralisation - Acids react with bases, alkalis, reactive metals and carbonates. This is called a neutralisation reaction.

Acid + Alkali -> Salt + Water
Acid + Base -> Salt + Water
Acid + Metal -> Salt + Hydrogen
Acid + Carbonate -> Salt + Water + Carbon Dioxide

Neutron - is an atomic particle found in the nucleus. It is similar in mass to a proton but has no charge.

Newton (N) - is the unit of force.

Nocturnal - active during the night.

Observations - the things that can be seem, watched during an experiment and the taking of notes to record facts based on the experiment. Try using all your senses to notice what is happening.

Omnivores - are animals that eat both animals and plants.

Opaque - does not allow light through.

Orbit- the curved path taken by an object that moves round another object like a planet around the Sun.

Organism - (of animal, plant) a section or piece resembling a living creature in behaviour or structure.

Particles - are the extremely tiny parts (substances) that scientists believe everything is made up of.

Permeable - is a material which allows water or liquids to flow through.

Photosynthesis - is the process from which plants use or changes sunlight into energy from the sun to make their own food. This energy is their food which contains oxygen and glucose. [carbon dioxide + water = glucose + oxygen] (also seephotosynthesis definitions page)

Physical Change - is when you mix two substances and their particles become jumbled up together. They do not necessarily combine chemically unless the atoms in the molecules are rearranged - this change is a physical change only. This new substance is called a mixture and can usually be separated quite easily.

Physicist - a physicist needs to get units right in calculations.

Physical Quantity S.I. Units Symbol

Length Metres m
Mass Kilograms kg
Time Seconds s
Force Newtons N
Energy Joules J

Pipette - a thin glass or plastic tube used to measure liquids.

Planet - is a large body that orbits a star.

Plates - are huge sections of the Earth's crust which float on the mantle.

Pole - in magnetism, the strongest part of a magnet. The pole of a magnet that points towards magnetic North is called its North seeking pole.

Pollination - is to fertilise by the transfer of plant pollen. The wind, birds and bees can pass pollens around.

Predator - is an animal which hunts and kills other animals for their food.

Predicting - to say what you think is going to happen in an experiment or investigation.

Process - is a number of actions for making or doing something.

Properties - are what a material or substance is like and how it behaves. Describes how a substance behaves. It can describe any piece of the material (for example if a material is strong or soft).

Protein - are nitrogenous compounds that are essential for life.

Proton - is an atomic particle found in the nucleus. It is similar in mass to the neutron but has a positive charge.

Rachis - (of feather) is the hollow shaft and network of hooks and barbules belonging to a feather.

Ray - is a narrow beam of light.

Reaction - is something that happens in response to something else.

Reaction Time - is the time that elapses between an event occurring and aperson responding to the event.

Recycled - is when something is used again in a system.

Reflect - is to bounce something back from a surface.

Reflection - is the change in direction when light or other wave motion rebounds at a boundary between two materials.

Refraction - is the change in speed when light or other wave motions passes from one material into another. The change in speed causes a change in wavelength and may cause a change in direction.

Reliable - things that can be taken to be true.

Reptiles - are animals that live mainly on land and lay eggs with soft shell. They have dry, scaly skin and crawls along on their belly and have short legs.

Research - is an investigation or study to find out facts in order to reac a conclusion.

Residue - is something that remains behind or is left over.

Result - is what happens at the end of an experiment.

Rodent - is an animal with strong incisor (cutting teeth at the front).

Rusting- is an oxidation process of iron and steel. Iron and steel rust in the presence of oxygen (air) and water. Rust is hydrated iron(III) oxide. Rust damages metal parts so it is important to try to prevent it. One way is to alloy the iron and steel with other metals which resist rust. Stainless steel is an alloy of iron wiht other metals such as chromium and nickel. Tpresence of these other metals protects the stainless steel from corrosion and allows these metals to be used as kitchen sinks and cutlery.

Safety Specs - must be worn to protect your eyes from any danger.

Scale - is the marks on any measuring instrument.

Sedimentary - the material that has been deposited by wind or water. The matter that forms at the bottom of a liquid.

Sieve - is when you separate a solid or a liquid by using a sieve.

Slaked lime - calcium hydroxide.

Soil - is the top layer of land on the Earth's surface.

Solar System - is a star and all the objects that orbit it.

Soluble - is the liquid that is produced after you have dissolved a solid into another liquid.

Solution - chemical: is the mixture of two or more substances, a solute dissolves in a solvent. The substance made when a solid disappears in a liquid. The process of solving a problem.

Specimen - is a sample of blood, urine or tissue which is used for analysis.

Spectrum - the range of colors that make up white light is called the spectrum. White light is a mixture of colors. When splitting light throught a prism you can see the spectrum of colors.

Stalactite - is a hanging formation of calcium carbonate dripping down from the roof of a cave.

Stalagmite - is the opposite of a stalactite; as it rises like a spike from the floor of a cave.

Star - is an astronomical object that generates energy due to nuclear fusion. A star gives out light and/or other forms of electromagnetic radiation.

Static Electricity - is an unbalanced charge that is not moving. A common cause of static electricity is the transfer of electrons when two objects are rubbed together. The object that gains electrons becomes charged negatively while the object that loses electrons becomes charged positively.

Stem - is the long, thin, supportive central part of a plant which bears a flower, fruit or leaf.

Symmetrical - is two halves that are mirror images of each other like butterfly wings.

Synthetic - is a substance or material which is not made up of natural substances like cotton or wool, but are man-made artifically from chemical reactions.

Tectonic plates - huge sections of the Earth's crust and upper mantle.

Temperature - is a measure of how hot or cold an object is.

Texture - is the appearance, feel and structure of a substance.

Thermometer - is an instrument used to measure temperature.

Tsunami - a large wave caused by an underwater eathquake or volcanic eruption.

Universe - is everything that exists.

Variables - are the things that can change during an experiment. Something that can vary during an experiment.

Vertebrates- are animals with a backbone.

Volume - is how much room something takes up. It is measured in centimeters (cm3).

Wasted energy - energy that is not usefully transferred or transformed.

Waterproof- does not allow water to pass through.

Wavelength - the distance from one wave peak to the next wave peak along the waves.

Weight - is a force due to gravity acting on an object.

X-rays - are used to detect broken bones. very penetrating, short wavelength electromagnetic waves.

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Kids Science word Dictionary Definitions and Explanations

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Absorbent - a substance that can soak up a liquid, or to take in energy and retain it. Absorber - an absorber does not reflect or transmit particles or radiation that hit it. Aluminium foil is an absorber of alpha particles. A dark, dull surface is an absorber of infra-red radiation.

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Look up word definitions

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Absorbent - a substance that can soak up a liquid, or to take in energy and retain it.

Absorber - an absorber does not reflect or transmit particles or radiation that hit it. Aluminium foil is an absorber of alpha particles. A dark, dull surface is an absorber of infra-red radiation.

Accuracy - is a term that refers to the properties of a measuring instrument.

Acid - an acid is a chemical that will neutralize a base such as an alkali. There are many different kinds of acid. Lemons are sour because they contain citric acid. Acid in vinegar is called acetic acid. It is a substance that disolves in water to form a solution with a pH below 7. An acid contains hydrogen which can be replaced by a metal to form a salt. When an acid dissolves in water H+(aq) ions are formed. A strong acid completely ionises in water and a weak acid only partly ionises. Common strong acids include hydochloric acid, HCl, sulphuric acid, H2SO4 and nitric acid, HNO3. A common weak acid is ethanoic acid, CH3COOH.

Acid rain - is a kind of pollution. Sulphur and nitrogen oxides are produced from the burning of fossil fuels. When they escape into the atmosphe, they form sulphuric and nitric acids. Thes acids can have effects on our environment, e.g. erode stonework, lower the pH of lakes and rivers killing our wildlife, and cause damage to trees.

Adhesive - made to stick like glue.

Air - is a mixture of gases.

Alkali - is a metal oxide or hydroxide (base) that dissolves in water to form a solution with a pH greater than 7. An alkali is neutralised by an acid to form a salt and water. Common alkalis include sodium hydroxide, NaOH, potassium hydroxide, KOH, calcium hydroxide, Ca(OH)2 and ammonium hydroxide, NH4OH.

Alloy - is a metal made by melting and mixing two or more metals together, e.g. brass is a mixture of copper and zinc and bronze is an alloy of copper and tin.

Amphibians - are animals that live in water and on land. They have smooth, moist skins and lay their eggs in water.

Antennae - a pair of sensory organs found on the heads of insects.

Apparatus - are the things (equipment) needed to carry out an experiment.

Aquatic - belonging to , or living in water.

Atomic - an atom is the smallest particle (unit of matter) of an element which can exist and be part of a chemical reaction (a source of nuclear energy). The tiniest part of a substance. Atomic is the use of atomic bombs or energy.

Bacteria - are very small single-celled organisms with no nucleus.

Balance/Top Pan Balance - is an instrument which is used to measure mass.

Barbule - branches that form from the hollow shaft (Rachis) of a feather. When birds preen (groom) their feathers they spread oils over them which 're-hooks' the barbules.

Battery - a battery consists of a number of electrical cells. These cells are usually connected in series to give a highter voltage than that from a sinlge cell.

Bedrock - solid rock immediatley beneath the surface soil.

Biodegradable - is a material that can rot and decay away quickly after we have used it.

Biologist - to study biology you will need to know the 7 life processes. A memory trick to remember what the life processes are is'MRS GREN'.

M - Movement - the moving parts of an organism

R - Reproduction - Producing offspring

S - Sensitivity - Reacting and responding to the environment

G - Growth - Increasing is size to adulthood

R - Respiration - Turning food into energy

E - Excretion - Getting rid of waste

N - Nutrition - Getting food to stay alive

Birds - are animals that have feather and wings. They lay eggs with hard shells and usually fly.

Bonded - Something that is bound, fastened or joined together.

Braided - interwoven hair and thread, or other fibres and yarns.

Bulb - part of the root of a plant which resembles a ball (e.g. onion).

Bunsen burner - is a gas burner used in a lab during experiments.

Canopy - a hanging cover forming a shelter.

Carnivores- are animals that eat other animals.

Catalyst - is something that alters the speed (speeds up) of a chemical reaction or change without being used up at the end of it or permanently changed itself.

Cells - one of the smallest parts of a plant or animal tissue.

Circuit - is one or more conducting paths between the two electrodes of a cell or battery of cells.

Characteristics - the distinguishing features or quality of something.

Chemicals - are the substances used in chemistry doing experiments..

Chemist - a chemist needs to be able to identify acids and alkalis. Universal Indicator can be used to show the pH of a substance.

Classifying - is to sort things into different groups.

Climate - the weather conditions of an area (e.g. the hot Siberian desert, the coldness of Iceland).

Compound - is a substance that has two or more elements in it.

Concave - describes the shape of a lens or other object where the center is thinner than the outside.

Conclusion - things that can be worked out from doing an experiment (making a decision). To draw to a close, to finish or conclude with an explanation, judgement or opinion based on interpretations.

Condensation - is the change from a gas to a liquid or solid.

Conifers - are relating to or part of trees or shrubs that do not have flowers and their seeds are made in cones.

Consistence - a degree of thickness or smoothness of a substance.

Controlled Variable - the things that you try to keep the same in an experiment or investigation.

Corrosion - is the wearing away of the surface of a metal by chemical reactions with oxygen and water. Rusting is one example of corrosion.

Crystals - a solid with a symmetrical arrangement of faces, usually bright and clear.

Current - is a flow of electric charge. The current is a metallic conductor is due to a flow of negatively charged electrons.

Data - a collection of observations, measurements and/or facts.

Decompose - the breaking down of parts from a whole - to decay or rot, wasting away.

Dense - made up of very closely packed particles.

Dilute - is to make a liquid weaker or thinner by adding more liquid, usually more water.

Dispersion - is the splitting of white light into the seven colors of the visible spectrum - rainbow.

Dissolving - is the process that occurs when a solute is added to a solvent and the solute disappears. The particles of the solute fit between the particles of the solvent. The solute can be recovered by the evaporation process. To mix a solid with a liquid so it becomes a liquid as well. To melt, to become a liquid (ice melting, sugar disolving in hot tea).

Distillation - this is to separate a liquid from other liquids by boiling it and condensing the steam. A substance that has been through an evaporation and condensing process.

Earth - is the planet that we inhabit. In electricity, the term refers to an electrical connection to the Earth.

Ecosystem - is the sum total of all the living organisms and non-living factors in an environment and the way they interact. The relationship between the environment, its animals and its plants.

Eiderdown - Eider is a duck which has very soft feathers, eiderdown is the down (feathers) from this duck.

Element - is a pure substance made of one kind of atom. It cannot be split up into anything simpler without losing its characteristics. A substance that cannot be separated into simpler substances.

Energy - is transfered by heating by; radiation, conduction and convection. The amount of energy transfered is measured in joules.

Environment - the conditions or surroundings in which people and animals live.

Enzymes - is a substance that speeds up a chemical reaction in the body (a biological catalyst). Each enzyme works best at a particular temperature and pH.

Erosion - is the process where rocks are worn away.

Evaluating - to decide if you have done something the best way and seeing what you could improve.

Evaporation - is the process in which a liquid changes to a vapour, due to particles leaving the surface of the liquid. A liquid turns to a gas. Changing from a liquid or a solid into vapours (gas).

Evidence - is anything that gives a reason to believe something.

Expand - is when the size of a substance increases due to being heated. The particles gain energy and move further apart.

Experiment - a test to find something out.

Explosion - is a very rapid reaction accompanied by a large expansion in gases.

Fabric - any material made of fibers or yarn which has been woven or knitted together.

Fair Test - is controlling some of the things used or done in a test so they do not change. An experiment in which only one variable is changed at a time to allow a fair comparison.

Felt - is tightly matted fabric made of wool which has had the fibers worked together under pressure.

Ferns - a plant with strong stems, roots and leaves and do not have seeds.

Fertilize - to provide a plant with pollen to bring about fertilization.

Filaments - are single stands of fiber.

Filter - is to separate solids (that do not dissolve) from liquids.

Fish - are cold-blooded animals that live in water, they have a backbone, scaly skin, tails and fins for swimming and gills for breathing.

Flammable - a substance or material that easily sets on fire.

Flowering Plants- any plant that produces flowers and fruit.

Force - is a push or pull. Force is measured in units called newtons (N).

Formula - is a way of writing scientific information using letters, numbers and signs.

Friction - occurs when two surfaces move over each other. Air resistance and water resistnace are friction forces caused by the movement of something through the air or the water.

Freeze - is when you cool something to a very low temperature and it usually forms ice.

Function - is the special purpose or use of something.

Galaxy - is a group of millions of stars held together by gravity, like the Milky Way.

Gas - is a state of matter in which the particles move rapidly and are very spread out.

Gravity - is the force of attraction between any two bodies. It increases with increasing mass of the bodies and decreases if they are further apart.

Habitat - is a place where an organism lives. It is the natural home of a plant or animal.

Herbivores - are animals that eat only plants.

Humidity - is warm dampness, it is a measure of the amount of water in the air.

Humus - bits of decaying plants and animals found in soil.

Igneous - (of rock) is the matter formed as moulten (entremely hot liquid) rock cools and hardens.

Indicator - is a chemical that can show if a substance is acidic or alkaline by changing color. Color turns red in acid and blue in alkali.

Infiltration - is the passing of a liquid or gas through a substance by means of a filter.

Insoluble - this is when a solid is unable to dissolve into a liquid.

Insulator - halts the passage of electricity, heat or sound through an object or substance.

Invertebrates - are animals without a backbone, such as worms.

Investigating - is to look for clues and try to work out what they mean.

Joule (J) - is the unit for measuring energy or work.

Kaleidoscope - is a tube filled with colored paper, which is lined with mirrors placed at different angles. Turning the tube will create amazing patterns for you to see through a small hole at the end of the tube.

Keratin - is a fibrous protein found in hair and nails.

Kinetic Energy - is the kind of energy in moving things.

Larva, larvae - is an insect that is still in its caterpillar state.

Leaf - is a flat green blade attached to the stem of a plant.

Lichen - is a mutualistic relationship between a fungus and an alga (simple plant). They can be seen as crusty patches on tree trunks and walls.

Liquid - is a state of matter in which the particles are close together but randomly arranged. The particles can move over each other.

Magnetic - applies to any object or material that is repelled or attracted by a magnet. Magnetic materials include iron, steel, cobalt and nickel.

Magnetic field - is an area where a magnetic material experiences a force. Magnetic fields exist around permanent magnets, electromagnets and electric currents.

Magnification - to be magnified. To increase the size of an object to make it bigger than it actually is.

Mammals - are animals that are warm-blooded, usually have fur or hair and feed their young with milk from their mother.

Matter - is the material that something is made up of.

Melting - is when a solid changes to a liquid at the melting point by heating.

Melting Point - is when the temperature at which a solid changes to a liquid.

Measuring Cylinder - is an instrument that measures the volume of a liquid.

Metamorphic - (of rock) is a complete change from its original state caused by heat and pressure.

Method - is an orderly way of doing something.

Methodology - is a scientific study of method. A system of methods used in a particular activity.

Microbes - are very small living things, usually only one cell big. A tiny organism that can only be seen with a microscope. Some microbes can cause disease.

Milky Way - is the spiral galaxy of stars which the Earth is part of.

Minibeasts - are miniature or very small animals such as insects.

Mixture - is two or more substances mixed together without actually joining them so that they can be separated again.

Molecule - is a group of atoms joined together.

Moss - a plant that has weak roots, thin, delicate leaves and do not have seeds.

Moult - is the shedding or casting off of feathers, hair, fur and skin.

Nectar - is the sweet juice of flowers from which bees make their honey.

Neutralisation - Acids react with bases, alkalis, reactive metals and carbonates. This is called a neutralisation reaction.

Acid + Alkali -> Salt + Water
Acid + Base -> Salt + Water
Acid + Metal -> Salt + Hydrogen
Acid + Carbonate -> Salt + Water + Carbon Dioxide

Neutron - is an atomic particle found in the nucleus. It is similar in mass to a proton but has no charge.

Newton (N) - is the unit of force.

Nocturnal - active during the night.

Observations - the things that can be seem, watched during an experiment and the taking of notes to record facts based on the experiment. Try using all your senses to notice what is happening.

Omnivores - are animals that eat both animals and plants.

Opaque - does not allow light through.

Orbit- the curved path taken by an object that moves round another object like a planet around the Sun.

Organism - (of animal, plant) a section or piece resembling a living creature in behaviour or structure.

Particles - are the extremely tiny parts (substances) that scientists believe everything is made up of.

Permeable - is a material which allows water or liquids to flow through.

Photosynthesis - is the process from which plants use or changes sunlight into energy from the sun to make their own food. This energy is their food which contains oxygen and glucose. [carbon dioxide + water = glucose + oxygen] (also seephotosynthesis definitions page)

Physical Change - is when you mix two substances and their particles become jumbled up together. They do not necessarily combine chemically unless the atoms in the molecules are rearranged - this change is a physical change only. This new substance is called a mixture and can usually be separated quite easily.

Physicist - a physicist needs to get units right in calculations.

Physical Quantity S.I. Units Symbol

Length Metres m
Mass Kilograms kg
Time Seconds s
Force Newtons N
Energy Joules J

Pipette - a thin glass or plastic tube used to measure liquids.

Planet - is a large body that orbits a star.

Plates - are huge sections of the Earth's crust which float on the mantle.

Pole - in magnetism, the strongest part of a magnet. The pole of a magnet that points towards magnetic North is called its North seeking pole.

Pollination - is to fertilise by the transfer of plant pollen. The wind, birds and bees can pass pollens around.

Predator - is an animal which hunts and kills other animals for their food.

Predicting - to say what you think is going to happen in an experiment or investigation.

Process - is a number of actions for making or doing something.

Properties - are what a material or substance is like and how it behaves. Describes how a substance behaves. It can describe any piece of the material (for example if a material is strong or soft).

Protein - are nitrogenous compounds that are essential for life.

Proton - is an atomic particle found in the nucleus. It is similar in mass to the neutron but has a positive charge.

Rachis - (of feather) is the hollow shaft and network of hooks and barbules belonging to a feather.

Ray - is a narrow beam of light.

Reaction - is something that happens in response to something else.

Reaction Time - is the time that elapses between an event occurring and aperson responding to the event.

Recycled - is when something is used again in a system.

Reflect - is to bounce something back from a surface.

Reflection - is the change in direction when light or other wave motion rebounds at a boundary between two materials.

Refraction - is the change in speed when light or other wave motions passes from one material into another. The change in speed causes a change in wavelength and may cause a change in direction.

Reliable - things that can be taken to be true.

Reptiles - are animals that live mainly on land and lay eggs with soft shell. They have dry, scaly skin and crawls along on their belly and have short legs.

Research - is an investigation or study to find out facts in order to reac a conclusion.

Residue - is something that remains behind or is left over.

Result - is what happens at the end of an experiment.

Rodent - is an animal with strong incisor (cutting teeth at the front).

Rusting- is an oxidation process of iron and steel. Iron and steel rust in the presence of oxygen (air) and water. Rust is hydrated iron(III) oxide. Rust damages metal parts so it is important to try to prevent it. One way is to alloy the iron and steel with other metals which resist rust. Stainless steel is an alloy of iron wiht other metals such as chromium and nickel. Tpresence of these other metals protects the stainless steel from corrosion and allows these metals to be used as kitchen sinks and cutlery.

Safety Specs - must be worn to protect your eyes from any danger.

Scale - is the marks on any measuring instrument.

Sedimentary - the material that has been deposited by wind or water. The matter that forms at the bottom of a liquid.

Sieve - is when you separate a solid or a liquid by using a sieve.

Slaked lime - calcium hydroxide.

Soil - is the top layer of land on the Earth's surface.

Solar System - is a star and all the objects that orbit it.

Soluble - is the liquid that is produced after you have dissolved a solid into another liquid.

Solution - chemical: is the mixture of two or more substances, a solute dissolves in a solvent. The substance made when a solid disappears in a liquid. The process of solving a problem.

Specimen - is a sample of blood, urine or tissue which is used for analysis.

Spectrum - the range of colors that make up white light is called the spectrum. White light is a mixture of colors. When splitting light throught a prism you can see the spectrum of colors.

Stalactite - is a hanging formation of calcium carbonate dripping down from the roof of a cave.

Stalagmite - is the opposite of a stalactite; as it rises like a spike from the floor of a cave.

Star - is an astronomical object that generates energy due to nuclear fusion. A star gives out light and/or other forms of electromagnetic radiation.

Static Electricity - is an unbalanced charge that is not moving. A common cause of static electricity is the transfer of electrons when two objects are rubbed together. The object that gains electrons becomes charged negatively while the object that loses electrons becomes charged positively.

Stem - is the long, thin, supportive central part of a plant which bears a flower, fruit or leaf.

Symmetrical - is two halves that are mirror images of each other like butterfly wings.

Synthetic - is a substance or material which is not made up of natural substances like cotton or wool, but are man-made artifically from chemical reactions.

Tectonic plates - huge sections of the Earth's crust and upper mantle.

Temperature - is a measure of how hot or cold an object is.

Texture - is the appearance, feel and structure of a substance.

Thermometer - is an instrument used to measure temperature.

Tsunami - a large wave caused by an underwater eathquake or volcanic eruption.

Universe - is everything that exists.

Variables - are the things that can change during an experiment. Something that can vary during an experiment.

Vertebrates- are animals with a backbone.

Volume - is how much room something takes up. It is measured in centimeters (cm3).

Wasted energy - energy that is not usefully transferred or transformed.

Waterproof- does not allow water to pass through.

Wavelength - the distance from one wave peak to the next wave peak along the waves.

Weight - is a force due to gravity acting on an object.

X-rays - are used to detect broken bones. very penetrating, short wavelength electromagnetic waves.

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Kids Science word Dictionary Definitions and Explanations

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Absorbent - a substance that can soak up a liquid, or to take in energy and retain it. Absorber - an absorber does not reflect or transmit particles or radiation that hit it. Aluminium foil is an absorber of alpha particles. A dark, dull surface is an absorber of infra-red radiation.

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Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

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Slipping, Sliding Science! | Physics for Kids

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Swings, Slides, and Science | Physics for Kids

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The laws of physics can be directly referenced when examining how a playground slide works. Several forces have an effect on the efficiency of a slide, with the most obvious being the force of gravity. Gravity is a constant force that exerts itself on anything that has mass.

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How do you like to go up in a swing,
Up in the air so blue?
Oh, I do think it the pleasantest thing
Ever a child can do!

Up in the air and over the wall,
Till I can see so wide,
River and trees and cattle and all
Over the countryside--

Till I look down on the garden green,
Down on the roof so brown--
Up in the air I go flying again,
Up in the air and down!
-- Robert Louis Stevenson

Very likely everyone who ever reads this page will already know how to operate a swing (and most will already have seen the poem quoted above). But why does it work? The answer may seem obvious ... until one thinks about it.

On this page I take a look at a qualitative explanation for the operation of a swing suspended by a single rope or chain on each side. A swing suspended by rigid rods, such as a typical lawn swing, is a little different in its principle of operation, though exactly the same motions will work to get it going.

Throughout this page, I will assume we're watching someone on a swing from their right side. When they're swinging forward, they're following a circular path around the bar going counter-clockwise. When they're moving back, they're revolving along the same circular path going clockwise.

Energy

Riding a swing is a lot like riding a pendulum. As the pendulum rises, its kinetic energy changes to potential energy; as it falls, the potential energy changes back to kinetic energy. The only way to increase the height of the swing is to increase the total energy of the pendulum.

Where's the energy coming from to "pump up" a swing? You can't give yourself any kind of direct "push"; there is nothing to push against. Furthermore, you normally only change position at the ends of the path, when you're at the top of the arc and momentarily stationary; energy is force times distance, and an impulse at zero velocity transfers no energy.

The only place we can reasonably expect to find the energy coming from is gravity. Somehow, at the ends of the arc, when you change position, you must be lifting yourself slightly, and thus increasing your potential energy at the moment when your kinetic energy is least.

But how is this done? Where's the "lift" coming from?

The Motions

The first thing we observe is that the motions of a person on a swing are normally symmetric. At the peak of the back-swing, the head and body go back, the legs go forward. At the front, the head and body go forward, the legs go back. One might speculate that this motion represents a However, either motion by itself is adequate to drive the swing. The symmetric motions aren't necessary. If you sit in a (slightly moving) swing and just tilt your head back and forth in the usual rhythm, while keeping your legs and body rigid, the swing will respond. (I've tried it.) Similarly, if you keep your head and body rigid and just swing your lower legs back and forth in the usual rhythm, the swing will respond.

Note well: Your head and shoulders are above your center of mass. Your feet and lower legs are below your center of mass. When you're on the swing, your center of mass is between your shoulders and your knees; your head and shoulders are closer to the bar (or "axle"), and your lower legs are farther from the bar, than your center of mass.
At the back of the arc, you throw your head back, but you throw your feet forward. What do these have in common? Both gestures apply a torque to your torso. More on this a little later.

The Line of Pull

The next thing to notice is that the line of pull is not through your center of mass, save at the very bottom of the arc. This is probably not obvious.

Consider what's going on: At the top of the arc, you are momentarily stationary; in particular, your body is not rotating. Your angular momentum is zero.

At the bottom of the arc, when you're traveling forward, your body is also rotating. Viewed from the right side, you are rotating counter-clockwise as well as moving forward (else your feet couldn't wind up out there in front of the rest of you at the top of the arc in front). So, if we take your center of mass as the origin, you've got "positive" angular momentum (the counterclockwise direction is typically designated as "positive"). If you're traveling backward, you're rotating clockwise, and you've got negative angular momentum. Angular momentum is conserved; something must have applied a torque to you, about your center of mass. What?

In figure 1, we see a figure on a stationary swing, hanging straight down. The line of pull of the chain is through the center of mass. Gravity, of course, always pulls straight down on the center of mass. So, the figure feels no net torque at that moment.

There are two forces acting on you. Gravity can only pull your center of mass straight down; with your center of mass as the origin, gravity can't apply a torque to you. So the torque must come from the other force, which is the pull of the chain. It must not be pulling through your center of mass. In figures 2 and 3, we see the same figure, not moving (not "pumping" the swing), but swinging passively back and forth like a pendulum. None the less, the body of the "pendulum swinger" rotates counter clockwise as the swing goes forward, and clockwise as the swing goes backwards. So, the swinger must be feeling a torque, and that must be coming from the chain. Hence, the line of pull must be as shown in figures 2 and 3. Note that the chain does not go straight from the bar to the swing: At the "pivot point", where the swinger is holding it, it bends. From experience, holding onto the chain is necessary to keep from falling off the swing; the swinger puts a "downward" force on the chain at that point; the line of pull goes straight from the swinger's hand to the bar.

Figure 1:
Figure 2:

Figure 3:

To summarize, on the back-swing, you're rotating clockwise (the "negative" direction). After you pass the low point, you're slowing down, and so is your rotation. After you pass the peak of the arc in back, you're rotating counter-clockwise, and your rotation is accelerating. So, throughout the back half of your swing, your angular momentum is increasingly positive, and the pull of the chain must be in front of your center of mass. By a similar argument, during the "front" half of your swing, the pull of the chain must be behind your center of mass.
To put that differently, everywhere except the bottom of the arc, the pull of the chain is along a line which passes below your center of mass.

Where the Lift Comes From

At the peak of the arc going back, you throw your head back and your feet forward. With your center of mass as origin, you're applying a positive (counterclockwise) torque to your head and feet; your torso, and the swing itself, experience a negative (clockwise) torque as a result. But the swing doesn't twist (much!) in response to this torque, so something must be applying an opposite torque to it. That "something" can only be one thing: The chain. It's pulling below your center of mass; to apply a positive torque to the swing and your torso (to keep them from twisting as you lean back and move your feet forward), the chain must be pulling harder. So, when you throw your head back and feet forward, and hence increase their angular momentum (as they move), you actually give a tug on the chain, and your center of mass lifts slightly ( figure 4).

Figure 4:

Let's go over that again a little more carefully. The chain is pulling toward the bar, which is normally above you at all points in your arc. So, that extra tug from the chain has a vertical component: It lifts your center of mass, very slightly. Look carefully at figure 4. As the swinger's head goes back and feet go forward, the swinger's body feels a "reaction torque" in the opposite direction. The result is increased pressure exerted by the swinger's hand on the pivot point, which consequently moves clockwise around the swinger's center of mass. By simple trigonometry, the swinger's center of mass must consequently move toward the bar.

To view it differently, by throwing your head back and feet forward at the back of the arc, you're "rolling yourself up" in the chain a little bit. In effect, you're pulling your center of mass up the chain.

The net consequence is that you gain a little potential energy, which comes back as kinetic energy when you swing down. At the bottom of the arc, you're going faster than you would have been had you not changed position.

At the front peak of the arc, you do the same thing, in reverse, and because the chain is now pulling behind your center of mass, you again end up being lifted slightly ( figure 5). So, you gain energy at both ends of the arc.

Figure 5:

You may object that if you "roll yourself up" in the chain a little, and so lift yourself that way, you must unroll at some point. When does that happen? The answer is, as you come down. At the bottom of the arc, the line of pull is once again through your center of mass. At that point, you've "unrolled" again from the chain and the extra potential energy has turned into kinetic energy, and the extra bit of torque from the chain has resulted in increased angular momentum at that point.

What If You Go "Over the Bar"?

What if you swing so high you go all the way around? Legend has it you'll turn inside out.

For all we know, the legend could be true -- for you can't go over the bar!

As soon as your arc reaches 180 degrees, so that the pull of the chain no longer has a vertical component at the peaks of the arc, the pumping will stop working. There is no way to "pull yourself up" the chain if the chain points down. (But note that there's no way to verify this with a simple experiment because of the issue outlined in the next paragraph...)

Furthermore, as soon as your arc exceeds 180 degrees, your velocity vector as you near the peak of the arc on the backswing is actually pointing forward, and your velocity vector once you pass the horizontal in front is pointing backward. As a result, you won't come back down a nice, clean arc - you'll come down in a parabolic fall until you use up the slack in the chain, at which point your path will make a sharp angle; that will cost energy because, for a moment, the pull of the chain will have a component pointing back along your path. So swinging is self-limiting: you can't go past the horizontal in front or in back.

But note that this argument only applies to swings supported by flexible ropes or chains. The rest of this discussion on this page applies, with small changes, to rigid rod-supported swings, but this section most assuredly does not: I have actually seen a rod-supported "swing device" at an amusement park driven a full 360 degrees by determined occupants! (They didn't turn inside out.)

Page created on 9/5/05. Updated with corrected diagrams on 9/6/05.

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How do you like to go up in a swing, Up in the air so blue? Oh, I do think it the pleasantest thing Ever a child can do!

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Balanced & Unbalanced Forces

What you will learn from this video What you will learn

Force has both strength and direction.

Unbalanced forces cause an object to change its motion.

Balanced forces do not cause a change in motion.

In a game of tug-o-war, what might cause the forces to become unbalanced?

Describe the two properties of forces.

Describe 1 situation with balanced forces and 1 situation with unbalanced forces.

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Learn about balanced and unbalanced forces! Our fun science video for kids will teach you what happens when two balanced forces come together. Watch now!

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FORCE & MOTION How Things Move *Explained* | Science for Kids!