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Physics > Energy > Flashcards

Energy Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

What is kinetic energy

A

The energy stored in moving objects

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2
Q

Equation for kinetic energy

A

Ek(J) = 0.5 x m(kg) x v^2(m/s)

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3
Q

What is elastic potential energy

A

Energy stored in a stretched object

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4
Q

Equation for elastic potential energy

A

Ee(J) = 0.5 x k(N/m) x e^2(m)

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5
Q

What is gravitational potential energy

A

The energy stored in an object due to its position above the Earth’s surface

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6
Q

Equation for gravitational potential energy

A

Ep(J) = m(kg) x g(N/kg) x h(m)

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7
Q

What is the specific heat capacity

A

The amount of energy required to raise the temperature of 1kg of the substance by 1 degree Celsius

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8
Q

Equation for specific heat capacity

A

Change in thermal energy(J) = m(kg) x c x temperature change (degrees Celsius)

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9
Q

What is thermal energy

A

Energy stored due to an objects temperature

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10
Q

What is the law of conservation of energy

A

Energy can be transferred usefully, stored or dissipated but it cannot be created or destroyed

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11
Q

What is a system

A

An object or group of objects

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12
Q

What is a closed system

A

No energy can enter or leave

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13
Q

Describe energy transfers in a pendulum

A

At the top the mass has the maximum store of GPE
As it swings to the bottom GPE transferred to KE
The mass has the maximum KE store at the bottom of the swing
As the mass swings back up KE transferred to GPE

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14
Q

Explain how a pendulum eventually stops swinging

A

There is friction in the fixed point and as the pendulum passes through air particles
Friction causes energy to be transferred to thermal energy
So energy is being dissipated
This causes the pendulum to gradually swing with less energy and eventually stop

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15
Q

Explain ways we can reduce unwanted energy transfers

A

Use a lubricant to reduce friction
Remove the air particles

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16
Q

Explain energy transfers during a bungee jump

A

At the start of the jump all of the energy in the system is GPE
As the jumper falls energy transfers from GPE store to KE store
When the bungee rope just starts to tighten the KE store is now at its maximum
When the rope is fully extended the KE store is zero as the jumper is not moving
All the energy is transferred to EPE store
The bungee rope recoils and energy is transferred from EPE store back to KE store
As he moves back up energy is transferred from KE store back to GPE store
At the top all of the energy is now in the GPE store

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17
Q

Why doesn’t the jumper in the bungee jump never return back to the original position

A

Because energy is dissipated as thermal energy
Due to:
Friction with air particles
Stretching effects in bungee rope

18
Q

What is work done

A

Whenever energy is transferred from one store to another

19
Q

Equation for work done

A

Work done (J) = Force(N) x Distance(m)

20
Q

Explain the energy transfers when a car brakes

A

Kinetic energy when it’s moving
Brake presses against wheel causing friction
Kinetic energy store is transferred to thermal energy store in the brakes
This causes temperature of brakes increases
So the car slows down and stops

21
Q

What is power

A

The rate at which energy is transferred or the rate at which work is done

22
Q

What is the equation linking Energy transferred, power, time

A

Power (W) = Energy transferred (J)/ Time (s)

23
Q

What is the equation linking work done, power, time

A

Power (W) = Work done (J)/ time(s)

24
Q

What is the equation linking efficiency, total input energy, useful output energy

A

Efficiency = Useful output energy transfer/ total input energy transfer

25
Q

Equation linking total power output, efficiency, useful power output

A

Efficiency = useful power output/total power input

26
Q

What are the factors that affect the cooling of a building

A

Thermal conductivity
Thickness of walls

27
Q

What is thermal conductivity

A

The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across that material

28
Q

Explain why insulation is used

A

Insulating material has a very low thermal conductivity
Thsi reduces the overall thermal conductivity of the wall
So much less thermal energy passes through the walls and escapes from the house

29
Q

Explain why double glazed windows are used

A

Double glazed windows have a lower thermal conductivity
So less thermal energy can pass through and leave the house

30
Q

Explain how to reduce thermal energy escaping from the roof of a house

A

Loft insulation
This has a low thermal conductivity
Reducing the rate at which thermal energy passes through

31
Q

What are the fossil fuels

A

Coal
Oil
Gas

32
Q

Advantages of fossil fuels

A

They are reliable as they always provide energy when we need it
They release a great deal of energy
They are abundant and cheap
They are versatile

33
Q

Disadvantages of fossil fuels

A

Burning fossil fuels releases a large amount of carbon dioxide
They are non-renewable so they will eventually run out
They can release other pollutants

34
Q

Advantages of nuclear power

A

Once the nuclear power plant is running it does not release carbon dioxide, so it doesn’t contribute to climate change
It’s extremely reliable as it generates a lot of electricity when we want

35
Q

Disadvantages of nuclear power

A

Nuclear power plants contain dangerous radioactive materials. If there’s an accident these can be released into the environment
Decommissioning a nuclear power plant takes many years and it’s expensive
A nuclear power plant generates large amounts of radioactive waste which is very dangerous

36
Q

What is renewable energy

A

A renewable energy resource is one that is being replenished as it is used

37
Q

Examples of renewable energy resources

A

Wind power
Solar power
Hydroelectric power
Tidal power
Biofuels
Geothermal
Wave power

38
Q

Advantages of renewable energy resources

A

Resources Will never run out
Do not add any carbon dioxide to the atmosphere so don’t contribute to climate change

39
Q

Disadvantages of renewable energy resources

A

Wind power and solar power are not reliable as some days it’s not windy and solar power doesn’t work well on cloudy days
Hydroelectric power destroys habitats when dams are built
Hydroelectricity is only useful in countries with lots of rivers

40
Q

What are biofuels

A

They are produced from plant materials
Burning biofuels doesn’t add extra carbon dioxide to the atmosphere(carbon neutral)
We can use the, to power vehicles
However biofuel can cause the price of food to increase

Physics (7 decks)

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