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Watch this video introducing you to the idea of gravity

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Read through this page and make notes in your science book about what gravity is and how it affects us

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Watch this video showing some of the common errors people make when thinking about gravity and falling objects

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Sir Isaac Newton is credited with the discovery of Gravity

Watch this short video looking at what lead Newton to this discovery

What is the name of the Idea that Newton founded (The Law of .... )

Make notes in your science book about what you learn

(If interested there is more information about Newton in the section "Who was Sir Isaac Newton" found below)

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Watch Beyond the Big Bang: Sir Isaac Newton's Law of Gravity Clip - The Universe | HISTORY

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Watch the Beyond the Big Bang: Sir Isaac Newton's Law of Gravity video clip of HISTORY's series The Universe'. Find this and many more videos only on HISTORY.

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5) Dropping a feather and hammer on the moon

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5) Dropping a feather and hammer on the moon

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Does the moon have gravity?

Before you watch this video make a prediction and write it in your science book,             What will hit the ground first, feather or hammer? Can you explain why?

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6) What is the difference between Mass and Weight??

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6) What is the difference between Mass and Weight??

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Read through this page and make notes about what you think the key differences are between Mass and Weight?

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Article Category: Units |

Right girls and boys, it's time to dip our toes into the wonderful world of science and explore the difference between mass and weight.

Most of you already use these two words on an almost daily basis (especially if, like me, you're conscious of your weight and spend hours agonising over how much muscle mass you built during your last visit to the gym). But do you really know the difference between weight and mass?

Have you been confusing mass with weight? It's very easy to do when you're not entirely sure of how science actually defines them. Even though they're both linked, there is a basic difference. I've put together a fairly comprehensive description for you which, importantly, is written in layman's terms and not scientific babble! Here goes...

What is mass?

Mass is a scientific measure of the amount of matter an object is made up of. No matter where you are at given moment in time, mass is constant. So, whether you're walking to the shop to stock up on groceries or bouncing around on the moon, your mass is the same. Obviously, if you're on a diet that's not the answer you want to hear but don't panic - we'll get to the all-important definition of weight shortly.

Some other key points about mass

1. Mass is indestructible. As you've seen above, no matter where you are in the universe your mass will never change

2. Mass can never be zero. What we mean by this is that everything in the universe has mass. If it didn't it simply wouldn't exist

3. Mass is not related to gravity, centrifugal force, etc and these forces have no effect whatsoever on your mass

4. Mass is commonly measured in kilograms and grams.

Hopefully, the descriptions above have given you a good idea of what mass really is. Don't fall into the trap of thinking that this unit of measure is not important - it is. After all, without the huge mass that makes up planet Earth we'd have no gravity - a great way to save money on fuel as you can simply float to work, but not so great when you're trying to drink your morning espresso on your way to the office.

What is weight?

Weight is a form of measurement that is dependent on gravity and, unlike mass, your weight can vary depending on where you are in the universe.

Weight is a pretty important measure not only to dieters the world over but also to the scientists and egg heads who design things like space shuttles and boats - opposite end of the spectrum, but it's all about perspective.

But how can weight vary whilst mass has to remain constant? It's fairly simple: weight is a variable i.e. it can change based on the amount of gravitational pull an object exerts on a body. Scientists have defined weight using this equation:

Formula: Weight (W) = Mass (M) multiplied by gravitational acceleration (g). (W = mg)

Simple, right?

Some key points about weight

1. The weight of an object changes based on where it is. If you've decided to visit the moon to test out this theory then you'll find that, in a matter of hours, you will have slashed your weight by two thirds (in your face, Slimming World!)

2. Weight is a vector and its direction of pull is towards the centre of the planet you're stood on. What? Sorry, I did promise layman's terms: gravity, which is created by the mass of an object, moves towards the centre of the object and it is gravity that determines your, or any other object's, weight.

3. The weight of any given object can go up or down depending on the amount of gravity acting on it. More gravity - the heavier the object. Less gravity - the lighter the object.

4. Unlike mass, weight can be zero. An example of this is an astronaut floating in space - there's no gravity acting on his body and, therefore, he has no weight.

5. Weight is commonly measured in Newtons.

Mass and weight example - the moon

In the below example, we've featured an astronaut on earth and on the moon. The Moon's gravity is much less than the Earth's gravity - approximately one sixth. So, a 100 kg astronaut weighs 980N on Earth. On the Moon, the astronaut would weigh only 162.2N. However, the astronaut's mass is 100kg where-ever they are.

Weight on Earth: 100kg x 9.8m/s ² = 980N.
Weight on Moon: 100kg x 1.622 m/s ² = 162.2N.

The difference between mass and weight - clarification

Ok, hopefully we've cleared up any lingering doubts you may have about the whole mass vs weight debate - mass is a measure of the amount of matter in an object and weight is the amount of force that gravity has on an object. As you can see, it's not quite a clear cut topic, but do keep these points in mind and prepare to wow your friends and family with your newfound knowledge of the scientific arts.

If you want to convert between different units of mass and weight, why not use the weight conversion tool.

Written by James Redden

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Please rate this article using the star rater below. If there is anything missing from the article, or any information you would like to see included, please contact me.

Last update: 14 February 2018

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What Is The Difference Between Mass And Weight?

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Article Category: Units | Right girls and boys, it's time to dip our toes into the wonderful world of science and explore the difference between mass and weight. Most of you already use these two words on an almost daily basis (especially if, like me, you're conscious of your weight and spend hours agonising over how much muscle mass you built during your last visit to the gym).

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If Mass is made up of Matter, then what is Matter?

Look through the first 4 pages and make notes in your science book (What is matter, Solids, Liquids, Gases)

Continue further if interested

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What is matter? It is simply all the stuff around us, stuff that you feel and touch, see and smell. More here.

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Can we change our weight?

Can we change our mass?

What is the value of gravity on earth? Is this value different on the moon?

Read through this page  and record anything new you learn in your science book

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Is there gravity in space?

Watch this video showing what its like to be in zero gravity

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Brian Cox Experiences Zero Gravity! - World Space Week - Wonders of the Universe - BBC

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To celebrate World Space Week we're uploading clips from Wonders of the Universe with Professor Brian Cox. Professor Brian Cox takes on the story of the force that sculpts the entire universe - gravity. Starting with a zero gravity flight, Brian experiences the feeling of total weightlessness, and considers how much of an effect gravity has had on the world around us.

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10) Mass and Weight in the International Space Station

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10) Mass and Weight in the International Space Station

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Watch this video teaching you about mass and gravity in space

What is the International Space Station?

Record anything new you learn in your science book

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This video was downloaded from http://education.ssc.nasa.gov/mvw_intro_video.asp Sequence of videos: 1. Introduction 2. Stretching Mass 3. Air Powered Mass 4. Accelerating Mass 5. Closing

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11) What two things can change the strength of Gravity?

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11) What two things can change the strength of Gravity?

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The force of gravity effecting an object depends on two things..

Watch this video and use your science book to record what they are and how they effect gravity

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Gravity

I would like you to know that you are an attractive person. I realize that we've never met, yet I am certain that you are indeed attractive. Do you know how I can say this with such confidence? Because you, just like all objects we can see and touch, have mass.

Maybe I need to clarify something. When I'm talking about attractiveness, I'm not referring to the way you look. I'm talking about the attractive force called gravity. Gravity is the force that pulls objects with mass toward each other.

We know about gravity thanks to the work of Sir Isaac Newton. He's the early scientist that got hit on the head with a falling apple. He deduced that the apple fell to the ground because it was being acted on by the earth's attractive force, which he called gravity.

Newton's Law of Universal Gravitation states that all objects in the universe are attracted to each other through the force of gravity. Gravity affects everything in the universe, but the amount of gravity affecting an object depends on two things: the masses of the objects being attracted and the distance between the objects. In this lesson, we will take a look at how mass and distance affect gravity.

Mass

Mass is the measure of the amount of matter in an object. For example, a bowling ball and a ping pong ball are made up of matter. However, a bowling ball contains more matter than a ping pong ball and therefore has more mass. A good way to think about the relationship between mass and gravity is to think of the saying 'the bigger they are the harder they fall.' In other words, the gravitational force between objects increases as the masses of those objects increase.

The earth is an object with a lot of mass, so objects fall toward the center of the earth with a noticeable amount of force. This explains why it's easier to lift a ping pong ball over your head than it is to lift a bowling ball. The smaller mass of the ping pong ball means less gravitational pull to overcome. Keep in mind that the Law of Universal Gravitation states that all objects with mass have gravity. Therefore, the bowling ball and the ping pong ball are actually being pulled toward each other. However, their masses are much too small for us to notice the attraction.

This relationship between mass and gravity also explains why you can jump higher on the moon than you can on Earth. The moon has less mass than Earth; therefore, the moon's gravitational force is less than that of the earth. Astronauts leap and jump with ease on the moon because there's less gravity to pull them down.

Distance

Gravity is also affected by the distance between two objects. The thing to keep in mind is that the strength of gravity decreases if the distance between two objects increases. Remember how I said the bowling ball and the ping pong ball are attracted to each other through gravity? Well, if you move those two balls farther apart, the gravitational force pulling them together decreases rapidly. This rapid decrease in gravity as distance increases explains why you don't get sucked in by the sun's gravitational pull.

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the effects of mass & distance on gravity - video & lesson transcript | study.com

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The Effects of Mass & Distance on Gravity - Video & Lesson Transcript | Study.com

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I would like you to know that you are an attractive person. I realize that we've never met, yet I am certain that you are indeed attractive. Do you know how I can say this with such confidence? Because you, just like all objects we can see and touch, have mass.

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Space is a vacuum

What does this mean?

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Read this page and write in your science book what you think a vacuum is?

What would happen to you if you went out into the vacuum of space?

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Cosmos4Kids.com: Universe: Vacuum of Space

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Cosmos4Kids.com! This astronomy tutorial introduces the vacuum of space. Other sections include the galaxies, stars, and the Solar System

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14) How strong is gravity on other planets?

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14) How strong is gravity on other planets?

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Look through this page to find out about gravity on other planets

What is the value of gravity on Earth?

Rank the planets in order of how strong their gravity is

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Gravity is a fundamental force of physics, one which we Earthlings tend to take for granted. You can't really blame us. Having evolved over the course of billions of years in Earth's environment, we are used to living with the pull of a steady 1 g (or 9.8 m/s ²). However, for those who have gone into space or set foot on the Moon, gravity is a very tenuous and precious thing.

Basically, gravity is dependent on mass, where all things - from stars, planets, and galaxies to light and sub-atomic particles - are attracted to one another. Depending on the size, mass and density of the object, the gravitational force it exerts varies. And when it comes to the planets of our solar system, which vary in size and mass, the strength of gravity on their surfaces varies considerably.

For example, Earth's gravity, as already noted, is equivalent to 9.80665 m/s ² (or 32.174 ft/s ²). This means that an object, if held above the ground and let go, will accelerate towards the surface at a speed of about 9.8 meters for every second of free fall. This is the standard for measuring gravity on other planets, which is also expressed as a single g.

In accordance with Isaac Newton's law of universal gravitation, the gravitational attraction between two bodies can be expressed mathematically as F = G (m ¹m ²/r ²) - where F is the force, m1 and m2 are the masses of the objects interacting, r is the distance between the centers of the masses and G is the gravitational constant (6.674×10⁻¹¹ N m ²/kg ² ).

Based on their sizes and masses, the gravity on another planet is often expressed in terms of g units as well as in terms of the rate of free-fall acceleration. So how exactly do the planets of our solar system stack up in terms of their gravity compared to Earth? Like this:
Gravity on Mercury:
With a mean radius of about 2,440 km and a mass of 3.30 × 1023 kg, Mercury is approximately 0.383 times the size of Earth and only 0.055 as massive. This makes Mercury the smallest and least massive planet in the solar system. However, thanks to its high density - a robust 5.427 g/cm3, which is just slightly lower than Earth's 5.514 g/cm ³ - Mercury has a surface gravity of 3.7 m/s ², which is the equivalent of 0.38 g.
Gravity on Venus:
Venus is similar to Earth in many ways, which is why it is often referred to as "Earth's twin". With a mean radius of 4.6023×10 ⁸ km ², a mass of 4.8675×10 ²⁴ kg, and a density of 5.243 g/cm ³, Venus is equivalent in size to 0.9499 Earths, 0.815 times as massive, and roughly 0.95 times as dense. Hence, it is no surprise why the gravity on Venus is very close to that of Earth's - 8.87 m/s ², or 0.904 g.
Gravity on the Moon:
This is one astronomical body where human beings have been able to test out the affects of diminished gravity in person. Calculations based on its mean radius (1737 km), mass (7.3477 x 10 ²² kg), and density (3.3464 g/cm ³), and the missions conducted by the Apollo astronauts, the surface gravity on the Moon has been measured to be 1.62 m/s ² , or 0.1654 g.
Gravity on Mars:
Mars is also similar to Earth in many key respects. However, when it comes to size, mass and density, Mars is comparatively small. In fact, its mean radius of 3.389 km is the equivalent of roughly 0.53 Earths, while its mass (6.4171×10 ²³ kg) is just 0.107 Earths. Its density, meanwhile, is about 0.71 of Earths, coming in at a relatively modest 3.93 g/cm ³. Because of this, Mars has 0.38 times the gravity of Earth, which works out to 3.711 m/s ².
Gravity on Jupiter:
Jupiter is the largest and most massive planet in the solar system. Its mean radius, at 69,911 ± 6 km, makes it 10.97 the times the size of Earth, while its mass (1.8986×10 ²⁷ kg) is the equivalent of 317.8 Earths. But being a gas giant, Jupiter is naturally less dense than Earth and other terrestrial planets, with a mean density of 1.326 g/cm ³.

Gravity anomalies on Mercury-mass concentrations (red) suggest subsurface structure and evolution. Credit: NASA/Goddard Space Flight Center/Johns Hopkins University/Carnegie Institution of Washington

What's more, being a gas giant, Jupiter does not have a true surface. If one were to stand on it, they would simply sink until they eventually arrived at its (theorized) solid core. As a result, Jupiter's surface gravity (which is defined as the force of gravity at its cloud tops), is 24.79 m/s, or 2.528 g.
Gravity on Saturn:
Like Jupiter, Saturn is a huge gas giant that is significantly larger and more massive than Earth, but far less dense. In short, its mean radius is 58232±6 km (9.13 Earths), its mass is 5.6846×10 ²⁶ kg (95.15 times as massive), and has a density of 0.687 g/cm ³. As a result, its surface gravity (again, measured from the top of its clouds) is just slightly more than Earth's, which is 10.44 m/s ² (or 1.065 g).

Mars Gravity Model 2011, showing variations of gravity accelerations over Mars's surface. Credit: geodesy.curtin.edu.au

Gravity on Uranus:
With a mean radius of 25,360 km and a mass of 8.68 × 10 ²⁵ kg, Uranus is approximately 4 times the size of Earth and 14.536 times as massive. However, as a gas giant, its density (1.27 g/cm ³) is significantly lower than Earth's. Hence, why its surface gravity (measured from its cloud tops) is slightly weaker than Earth's - 8.69 m/s ², or 0.886 g.
Gravity on Neptune:
With a mean radius of 24,622 ± 19 km and a mass of 1.0243×10 ²⁶ kg, Neptune is the fourth largest planet in the solar system. All told, it is 3.86 times the size of Earth and 17 times as massive. But, being a gas giant, it has a low density of 1.638 g/cm ³. All of this works out to a surface gravity of 11.15 m/s ² (or 1.14 g), which again is measured at Neptune's cloud tops.

All in all, gravity runs the gamut here in the solar system, ranging from 0.38 g on Mercury and Mars to a powerful 2.528 g atop Jupiter's clouds. And on the Moon, were astronauts have ventured, it is a very mild 0.1654 g, which allowed from some fun experiments in near-weightlessness!

Understanding the effect of zero-gravity on the human body has been essential to space travel, especially where long-duration missions in orbit and to the International Space Station have been concerned. In the coming decades, knowing how to simulate it will come in handy when we start sending astronauts on deep space missions.

And of course, knowing just how strong it is on other planets will be essential to manned missions (and perhaps even settlement) there. Given that humanity evolved in a 1 g environment, knowing how we will fare on planets that have only a fraction of the gravity could mean the difference between life and death.

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Gravity is a fundamental force of physics, one which we Earthlings tend to take for granted. You can't really blame us. Having evolved over the course of billions of years in Earth's environment, we are used to living with the pull of a steady 1 g (or 9.8 m/s2).

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Watch this video demonstrating how gravity can cause things to orbit

Why do all the planets orbit in the same direction?

Does the gravity of the moon effect the earth?

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Watch this video explaining how the tides are created

Draw a diagram in your book and explain how the moon and sun can cause the tides

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Read this page and make some notes

What is an eclipse?

What causes it?

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Below, check out a visualization of the April 8, 2024, total solar eclipse!

What's the difference between a lunar eclipse and a solar eclipse?

Solar Eclipse

A solar eclipse happens when the Moon gets in the way of the Sun's light and casts its shadow on Earth. That means during the day, the Moon moves over the Sun and it gets dark. Isn't it strange that it gets dark in the middle of the day?

This total eclipse happens about every year and a half somewhere on Earth. A partial eclipse, when the Moon doesn't completely cover the Sun, happens at least twice a year somewhere on Earth.

But not everyone experiences every solar eclipse. Getting a chance to see a total solar eclipse is rare. The Moon's shadow on Earth isn't very big, so only a small portion of places on Earth will see it. You have to be on the sunny side of the planet when it happens. You also have to be in the path of the Moon's shadow.

On average, the same spot on Earth only gets to see a solar eclipse for a few minutes about every 375 years!

Caution! Eye Safety During a Total Solar Eclipse
Except during the brief total phase of a total solar eclipse, when the Moon completely blocks the Sun's bright face, it is not safe to look directly at the Sun without specialized eye protection for solar viewing.

For safety information, visit the NASA Eclipse Safety Page.

Lunar Eclipse

During a lunar eclipse, Earth gets in the way of the Sun's light hitting the Moon. That means that during the night, a full moon fades away as Earth's shadow covers it up.

The Moon can also look reddish because Earth's atmosphere absorbs the other colors while it bends some sunlight toward the Moon. Sunlight bending through the atmosphere and absorbing other colors is also why sunsets are orange and red.

During a total lunar eclipse, the Moon is shining from all the sunrises and sunsets occurring on Earth!

Why don't we have a lunar eclipse every month?

You might be wondering why we don't have a lunar eclipse every month as the Moon orbits Earth. It's true that the Moon goes around Earth every month, but it doesn't always get in Earth's shadow. The Moon's path around Earth is tilted compared to Earth's orbit around the Sun. The Moon can be behind Earth but still get hit by light from the Sun.

Because they don't happen every month, a lunar eclipse is a special event. Unlike solar eclipses, lots of people get to see each lunar eclipse. If you live on the nighttime half of Earth when the eclipse happens, you'll be able to see it.

Remembering the Difference

It's easy to get these two types of eclipses mixed up. An easy way to remember the difference is in the name. The name tells you what gets darker when the eclipse happens. In a solar eclipse, the Sun gets darker. In a lunar eclipse, the Moon gets darker.

Related Resources for Educators

Launchpad: Solar Eclipses

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18) Whats the difference between a solar and lunar eclipse?

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18) Whats the difference between a solar and lunar eclipse?

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Watch this video and draw a diagram in your science book of both a solar and lunar eclipse

Whats the difference?

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What's the difference between a solar and lunar eclipse?

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Umbra - the fully shaded inner region of a shadow cast by an object (experiences the total phase of an eclipse)

Penumbra - the partially shaded outer region of the shadow cast by an object (experiences partial eclipse)

Given these definitions, can you label the umbra and the penumbra on the following picture?

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Play around with this simulator

Watch how the sun, earth and moon affect each others orbits

Can you re-create a solar eclipse?

What about a lunar eclipse?

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21) Just for Fun: Places where the Laws of Gravity don't seem to Exist!

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21) Just for Fun: Places where the Laws of Gravity don't seem to Exist!

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Watch this video showing  some mysterious places that seem to defy gravity

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5 Places Where Gravity Does Not Seem to Exist

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The popular story of Sir Isaac Newton states that he was sitting under an apple tree when an apple fell on his head, and he pondered for a bit before he thought of the universal law of gravitation.

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- Before you watch this discuss with a partner wether or not you believe man really did land on the moon..

- Do the same again after you watch this.

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- After watching this do you still hold the same thoughts about the moon landing?
Discuss this with a friend...

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Truth Behind The Moon Landings - Skeptics debunked - Documentary

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Complete this worksheet to test your knowledge on tides and eclipse

Ignore question one as we have not covered this

For questions relating to umbra and penumbra see that section in the padlet and ask the teacher to help explain if you are confused.

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phases eclipses and tides worksheet - Free download as PDF File (.pdf), Text File (.txt) or read online for free.

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- Complete this after watching the Martian
- Complete this assessment individually or in pairs.

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Read this if you are interested in how gravity is calculated

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In the 1600s, an English physicist and mathematician named Isaac Newton was sitting under an apple tree -- or so the legend tells us. Apparently, an apple fell on his head, and he started wondering why the apple was attracted to the ground in the first place.

Newton publicized his Theory of Universal Gravitation in the 1680s. It basically set forth the idea that gravity was a predictable force that acts on all matter in the universe, and is a function of both mass and distance. The theory states that each particle of matter attracts every other particle (for instance, the particles of " Earth" and the particles of "you") with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

So the farther apart the particles are, and/or the less massive the particles, the less the gravitational force.

The standard formula for the law of gravitation goes [source: UT]:

Gravitational force = (G * m1 * m2) / (d2)

where G is the gravitational constant, m1 and m2 are the masses of the two objects for which you are calculating the force, and d is the distance between the centers of gravity of the two masses.

G has the value of 6.67 x 10E-8 dyne * cm ²/gm ². So if you put two 1-gram objects 1 centimeter apart from one another, they will attract each other with the force of 6.67 x 10E-8 dyne. A dyne is equal to about 0.001 gram weight, meaning that if you have a dyne of force available, it can lift 0.001 grams in Earth's gravitational field. So 6.67 x 10E-8 dyne is a miniscule force.

When you deal with massive bodies like the Earth, however, which has a mass of 6E+24 kilograms (see How much does planet Earth weigh?), it adds up to a rather powerful gravitational force. That's why you're not floating around in space right now.

The force of gravity acting on an object is also that object's weight. When you step on a scale, the scale reads how much gravity is acting on your body. The formula to determine weight is [source: Kurtus]:

weight = m * g

where m is an object's mass, and g is the acceleration due to gravity. Acceleration due to gravity on Earth, is 9.8 m/s² -- it never changes, regardless of an object's mass. That's why if you were to drop a pebble, a book and a couch off a roof, they'd hit the ground at the same time.

For hundreds of years, Newton's theory of gravity pretty much stood alone in the scientific community. That changed in the early 1900s.

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In the 1600s, an English physicist and mathematician named Isaac Newton was sitting under an apple tree -- or so the legend tells us. Apparently, an apple fell on his head, and he started wondering why the apple was attracted to the ground in the first place.

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Read through this short page if you want to see calculations of how gravity can change as we get further away from the earth

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Read this if your interested in learning more about Sir Isaac Newton, the man who discovered gravity

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Isaac Newton | Biography, Facts, Discoveries, Laws, & Inventions

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Isaac Newton, the brilliant physicist and mathematician, revolutionized our understanding of the universe with his laws of motion and universal gravitation, forever changing the course of scientific inquiry.

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How to create your own demonstration of gravity

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Make your own: - 3/4 inch diameter PVC tubing with 1/8 inch thick walls. Usually comes in 100 foot coil for ~$12-$30 (find at local hardware store). To create a 60 inch diameter hoop, you'll want to cut a 188.5 inch length of tube.

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Create your own solar system and watch how the planets affect each others gravity

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Fling planets and change physics in this gravity sandbox. Want to add 1000 planets? Go ahead. Curious about Lagrange Points? Make em. Hate the inverse square law? Change it.

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This website contains heaps of values for comparing things like the sizes, weights and distances of all the planets and the sun

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Surface Gravity of the Planets and the Sun

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A simple animation showing how a spacecraft transfers from orbit around the Earth to an orbit around the Moon

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Click on the Flight to the Moon button to start the journey. First, the rocket orbits the earth several times. After a thrust impulse powerful enough to escape the Earth's gravity, you will see the rocket leave the Earth's orbit. It then follows the transfer orbit between the Earth and the Moon.

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World Space Week | Celebrate UN-declared World Space Week, 4-10 October annually, the largest space event in the world

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FOR IMMEDIATE RELEASE (December 22, 2023) - World Space Week Association today announced that the theme for World Space Week, October 4-10, 2024, will be "Space & Climate Change." "We will emphasize the essential role that space plays in monitoring the Earth's...