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group members: stephanie, hillary, jingxuan, zavier, jia an
forces of nature can cause natural disasters such as tropical cyclones, earthquakes, volcanic eruptions & tsunamis
earthquakes and volcanic eruptions that occur beneath the ocean may be strong enough to trigger a series of waves known as tsunamis
the potential energy of ocean water increases greatly as a result as the waves move at a high speed towards the shore, the potential energy in the waves is converted to kinetic energy.
forces in nature can also shape the physical environment and give rise to beautiful platforms

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9.2 What are the types of forces? [Alysha, Xi En, Carina, Fione, Xin Li]

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9.2 What are the types of forces? [Alysha, Xi En, Carina, Fione, Xin Li]

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Two categories

Contact

Applied force

Normal contact force

Tension

Friction [opposes motion between two surfaces]

Air resistance

Elastic [acting on stretched or compressed objects]

Non-contact

Gravitational force (weight) [attracts two objects towards each other]

Magnetic force [between a magnet and another magnetic material/ magnets]

electric force

Weight
measure of gravitational force exerted on an object

Newtons (N)

spring balance

no constant value

Mass
amount of matter in an object

Kilograms (Kg)

Electronic balance

constant value

Weight = mass x gravitational force

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9.3 What happens when two or more objects interact?

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9.3 What happens when two or more objects interact?

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names: Sze Tong, Zili, Sarah, Licia, Anya
Effects of forces on objects:
- move a stationary object
- change the speed of an object
- change the direction of an object
- stop a moving object
-can cause turning effect
-change the size and shape of an object
-pressure is an effect of force acting on an object.
-small area of contact = more pressure
-SI unit of pressure is pascal
-pressure = force/area
-when a force is applied and the object moves in the same direction as the force, work is done
-SI unit for energy is joules
Work is also done when energy is transferred from one form to another.....

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Total energy remains constant as energy is cannot be created or destroyed but transferred or converted from one object to another.

Example, on a rollercoaster, at the highest point, the rollercoater has maximum gravitational potential energy which means there is no kinetic energy. As the rollercoaster moves down the track, some gpe is converted to ke. At this point, there is some ke and some gpe but the total energy does not change.

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Temperature is the measure of how hot an object is.

SI unit: kelvin
unit we use : degree celcius (0c)

objects in contact

heat energy transferred from hotter to colder object

temperature

colder decrease
higher increase
until same temperature

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How heat transfer occur

Three ways heat transfer can occur :

-Conduction

-Convection

-Radiation

Conduction:

The transfer of heat energy without the physical movement of the medium.

Convection:

The transfer of heat energy from one place to another by the physical movement of a medium. Fluids transfer heat energy mainly by convection.

Radiation:

The transfer of energy from a hotter body to a colder one without the need of the presence of a matter.

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Chapter 10.4 - What affects the rate at which heat energy is transferred????????

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Chapter 10.4 - What affects the rate at which heat energy is transferred????????

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Presenter: tann sheng qing Lucas

In chapter 10.4, we are introduced to factors affecting the rate at which heat energy is transferred through conduction & radiation.

Factors affecting the rate of conduction is the material of the object. For example, wood is a poor conductor of heat, but steel is a good conductor of heat, therefore steel will get hotter than wood.

Solids are also better conductors of heat than liquids or gases.

Factors affecting the rate of radiation is the temperature of the object. The hotter an object, the higher the rate of radiation. Another factor is the surface area of an object. An object with a larger surface area has a higher rate of radiation, for example heat sinks on computers. The last factor is type of surface. An object with a darker surface, dull, & rough surfaces are better absorbers of radiation than white, smooth, & shiny surfaces.

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10.2 Effects of heat transfer

-Expansion and contraction in solids

Expansion gaps are left in joints to prevent buckling

Rollers are under bridges to allow expansion and contraction to take place safely

- Expansion in liquids

Climate change causes oceans to heat up and expand thus causing sea levels to rise

- Expansion and contraction in liquids and gas

Flexible bends allow metal pipes carrying steam and hot water allow pipes to expand

And contract without breaking

Bimetallic strip

It is made out of 2 metals that expand at different rates upon change in temperature

Are used in thermostats and in bimetallic strips