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Science :D > Chapter 9: Application of Forces and Transfer of Energy > Flashcards

Chapter 9: Application of Forces and Transfer of Energy Flashcards

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1
Q

Define ‘force”

A

It is a push or a pull

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2
Q

What can a force do?

A

It can cause great destructions during natural disasters

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3
Q

What are 7 effects of a force?

A
  1. Change the shape of an object
  2. Change the size of an object
  3. Change the direction of a moving object
  4. Change the speed of a moving object
  5. Start a stationary object moving
  6. Stop a moving object
  7. Cause a turning effect about a fixed point
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4
Q

What can’t a force do?

A

It cannot change the mass of an object. ( not adding or removing matter from the object)

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5
Q

What are the 4 types of forces?

A
  1. Frictional Force
  2. Elastic Force
  3. Gravitational Force
  4. Magnetic Force
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6
Q

Define ‘frictional force’

A

It is the force that opposes motion

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7
Q

Define ‘elastic force’

A

It is the force that acts on a stretched or compressed object to return it to its original shape

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8
Q

Define ‘gravitational force’

A

It is the force that attracts two objects towards each other

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9
Q

Define ‘magnetic force’

A

It is the force exerted between a magnet and another magnetic material or magnet

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10
Q

Is gravity a push or pull?

A

It is a pull

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11
Q

Define ‘contact force’

A

They are forces that act between two objects that are in physical contact with each other

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12
Q

Define ‘non-contact force’

A

They are forces that act between two objects that are not touching each other

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13
Q

What are the pros and cons of friction?

A

Pros: Allow us to walk without slipping and allows us to grip things
Cons: Causes wear and tear, more force is needed to overcome friction

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14
Q

What can you do to reduce friction?

A
  • Use lubricant
  • Use ball bearings
  • Use rollers
  • Use wheels
  • Use a layer of air
  • Having a streamlined body
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15
Q

What is mass?

A

It is the amount of matter in an object

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16
Q

What is weight?

A

It is the amount of gravity acting on an object.

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17
Q

What can mass be measured with?

A

Beam balance or electronic balance

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18
Q

What can weight be measured with?

A

Spring balance

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19
Q

What is the SI unit for mass?

A

kg

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20
Q

What is the SI unit for weight?

A

Newtons (N)

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21
Q

Define ‘pressure’

A

It is the force exerted per unit area.

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22
Q

What are the 2 relationships between force, area and pressure?

A
  1. Same force, smaller contact area, larger pressure
  2. Same contact area, larger force, larger pressure
    (vice versa)
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23
Q

What causes water pressure?

A

It is caused by the pressure exerted by the weight of the water above.

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24
Q

What is a characteristic for pressure in liquids? Why does it happen?

A

The pressure acts in all directions as liquid particles are free to move around

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25
Q

What causes atmospheric pressure?

A

It is caused by the pressure exerted by the layer of the air surrounding the Earth.

26
Q

When is atmospheric pressure lower?

A

When we are at a higher height

27
Q

Why is atmospheric pressure lower when we are at a higher height?

A

There are lesser air particles pushing down on us

28
Q

What are the conditions needed for work to be done?

A
  1. A force must be applied
  2. The object must move in the direction of the applied force.
29
Q

What are the non-renewable sources of energy?

A

Fossil fuels, biofuels, nuclear energy

30
Q

What are the renewable sources of energy?

A

Solar energy, hydroelectric energy, wind energy, geothermal energy

31
Q

How are fossil fuels formed?

A

They are formed by the remains of dead animals and plants that were buried in Earth millions of years ago.

32
Q

What causes fossil fuels to release heat energy?

A

The fossil fuels are burnt and they undergo a chemical process, releasing heat energy.

33
Q

What are some uses of heat energy produced by fossil fuels?

A

-The heat energy can be converted to other types of energy.
-For example, the heat energy released can be used to boil water to produce steam, which powers turbines to produce electricity.

34
Q

What is the impact of the use of fossil fuels on the environment?

A
  1. Burning of fossil fuels releases air pollutants and greenhouse gases into the environment.
  2. Those greenhouse gases can contribute to global warming.
  3. Those greenhouse gases can increase the rate of climate change
35
Q

What do solar panels do?

A

They capture sunlight and convert light energy into electrical energy.

36
Q

In Singapore, where are we going to install solar panels on?

A
  1. Rooftops
  2. Building facades
    3, Reservoirs
  3. Offshore sea spaces.
37
Q

What can solar energy be used in?

A

Solar-powered devices. (LED street lights and weather recording instruments.)

38
Q

What is the impact of solar energy on the environment?

A
  1. Able to generate electricity without releasing air pollutants and greenhouse gases.
  2. Toxic waste is generated during the production and disposal of solar panels.
39
Q

Define ‘hydroelectric energy’.

A

It is electrical energy generated by turbines when moving water powers them.

40
Q

How does a hydroelectric power station work?

A

1.Reservoir water stores GPE behind the dam.
2. As water runs down the turbine passageway at high speed, GPE is converted to KE.
3. As the moving water turns the blades of the turbines, the KE of the water is converted to the KE of the turning blades.
4. The KE of the turning blades of the turbine is converted to electrical energy in the generator.

41
Q

What is the impact of using hydroelectric energy on the environment?

A
  1. Generating hydroelectric energy produces very little greenhouse gases.
  2. Reservoir water floods area behind dam.
  3. The flood cause plant die and force animal to move to other areas.
  4. People who make a living by fishing have to relocate further inland.
41
Q

What do wind turbines do?

A

They convert wind energy into electrical energy.

41
Q

How does a wind turbine work?

A
  1. Wind blow at wind turbine, KE of wind transfer to blades or the turbine, causing the blades to rotate
  2. Generator connected to turbine spins and generates electrical energy.
42
Q

Define ‘geothermal energy’

A

It is heat that is stored in Earth.

42
Q

What is the impact of using wind energy on the environment?

A
  1. Large plots of land needs to be cleared to build wind farms.
  2. There will be a potential loss of wildlife as natural habitats are destroyed.
  3. Birds may get killed if they collide into the rotating blades of the wind turbines
  4. The noise produced by the rotating blades can also be a source noise pollution to nearby communities.
43
Q

What is geothermal energy used for?

A

It can be harnessed to generate electrical energy.

44
Q

How does a geothermal power plant work?

A
  1. Cooled water pump into hot rocks inside core
  2. Cooled water heat by GE and turn into steam
  3. Hot water and steam pump up to Earth surface
  4. Steam use to power the turbine and generator, produce EE
45
Q

What is the impact of using geothermal energy on the environment?

A
  1. Large areas of land need to be cleared
  2. Habitats of wildlife are destroyed.
  3. Diversity of species are affected
    4.Traces of toxic elements buried underground are drawn out
46
Q

What are biofuels made from?

A

Animal waste or plant materials that cannot be eaten by humans or recycled food waste.

47
Q

What is an example of a biofuel and what is it made from?

A

Ethanol, it is made from plants such as sugarcane and corn.

48
Q

What can biofuels be used for?

A

They can be used to power motor vehicles

49
Q

What happens when carbon dioxide that was released from the burning of biofuels goes into the atmosphere?

A

Plants will absorb the carbon dioxide when they make food.

50
Q

What is the use of biofuels on the environment?

A

Con: The burning of biofuels releases air pollutants into the environment.
Pro: Plants used to make biofuels can be grown in a short time. Biofuels can also be made from used cooking oil and other food waste.

51
Q

Define ‘nuclear energy’.

A

It is the energy harnessed from the nucleus of an atom.

52
Q

How can nuclear energy be obtained?

A

Through nuclear reactions and then be converted into electrical energy.

53
Q

How does a nuclear power plant work?

A
  1. Heavy atom split into smaller atoms, large amount of heat energy is released.
  2. Heat energy use to boil water
  3. Steam produced power turbine to generate EE
54
Q

What is the impact of nuclear energy on the environment?

A
  1. Source of clean energy
  2. Require less land space to generate same amount of energy compared to other alternative sources of energy
  3. Potential risks to health and safety of communities living near nuclear power plants.
55
Q

Why does an injection needle need to be very sharp? (Practice Question)

A

An injection needle needs to be very sharp so that the area of contact of the needle with the skin is very small. When we apply a force on the needle, a high pressure allows the sharp needle to pierce the skin easily.

56
Q

Why will the phone crack if I step on it with high heels but not when I wear sneakers? (Practice Question)

A

The heel of a high-heeled shoe has a smaller area of contact with a surface than the heel of a sneaker. The screen will likely crack due to the high pressure exerted on it if stepped on by high heels. However, the screen may not crack due to a lower pressure exerted on it.

57
Q

Why does a sharp knife cut a tomato easier than a blunt knife? (Practice Question)

A

A sharp knife has a smaller area of contact with the tomato than a blunt knife. With the same amount of force applied, the sharp knife exerts a higher pressure than a blunt knife, thus it is able to cut the tomato more easily.

58
Q

How does a straw work? (Practice Question)

A

When the straw is sucked, some air is removed from it. The air pressure inside the straw decreases and becomes lower than the surrounding atmospheric pressure. The higher atmospheric pressure pushes the liquid up the straw and into the our mouth.

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