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Physics > P1 > Flashcards

P1 Flashcards

1
Q

Give the four ways that energy can be transferred ?

A

Heating, waves, an electric current or when a force moves an object.

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2
Q

Give 5 examples of energy.

A

Chemical energy, Kinetic energy, Gravitational potential energy stores, elastic potential energy stores, thermal energy stores.

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3
Q

Where is chemical energy found and how is it transferred ?

A

Found in fuels, foods, or the chemicals found in batteries. Thus energy is transferred during chemical reactions.

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4
Q

What is kinetic energy ?

A

Kinetic energy stores describe the energy an object has because it is moving.

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5
Q

What is gravitational potential energy?

A

It is used to describe the energy stored in an object because of its position, such as an object above the ground.

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6
Q

What is elastic potential energy?

A

It describes the energy stored in a springy object when you stretch it or squash it.

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7
Q

What is a thermal energy store ?

A

It describes the energy a substance has because of its temperature.

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8
Q

What is the “The law of conservation of energy”

A

Energy cannot be created or destroyed but can only be transferred.

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9
Q

Describe the energy transference involved in a torch.

A

In a torch, the torch’s battery pushes a current through the bulb. this makes the torch bulb emit light, and also get hot.

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10
Q

Describe the energy transference involved in a kettle.

A

When an electric kettle is used to boil water, the current in the kettle’s heating element transfers energy to the thermal energy store of the water and the kettle.

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11
Q

When an object falls does it gain or lose speed?

A

It gains speed.

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12
Q

When an object falls does its store of gravitational potential energy increase or decrease ? (explain why)

A

Decrease because it’s getting closer to the ground.

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13
Q

What energy transfers happen to a bungee jumper instantaneously after jumping off the platform?

A

When the rope is loosely attached, energy is transferred from the gravitational potential store to the kinetic energy store as the jumper accelerates towards the ground due to the force of gravity.

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14
Q

What happens to the bungee jumper as the rope tightens as they fall towards the ground?

A

When the rope tightens, it slows down the bungee jumper’s fall. This is because the force of the rope reduces the speed of the jumper. The jumper’s kinetic energy store decreases and the rope’s elastic potential energy increases as the rope stretches.

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15
Q

What happens to the bungee jumper as they come to a stop when at max elasticity on the rope?

A

The energy that was originally in the kinetic energy store of the jumper has all been transferred into the elastic potential energy store of the rope.

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16
Q

You have to apply _____ to move something. The ____ you do causes a transfer of energy.

A

force

work

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17
Q

When an object is moved by a force, ____ is done on the object by the force.

A

work

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18
Q

The force acting upon the object transfers this ______ to the object.

A

energy

19
Q

TRUE OR FALSE…

The amount of energy transferred to the object is equal to the work done on it.

A

TRUE

20
Q

Give an example of work done on a object with values.

A

To raise an object you need to apply a force to it to overcome the force to it to overcome the force of gravity on it. If the work you do on the object is 20j, the energy transferred to it must be 20j. So its gravitational potential energy increases by 20j.

21
Q

What is the equation for work done including units?

A

Work done (W) =Force applied (F) * distance moved along the line of action (M)

22
Q

____ done to overcome ________ is mainly transferred to _______ energy stores by heating.

A

work
friction
thermal

23
Q

Describe the example of friction at work between your hands.

A

If you rub your hands together vigorously, they become warm. Your muscles do work to overcome the friction between your hands. The work you do is transferred as the energy that warms your hands.

24
Q

Describe the example of friction at work on your brake pads.

A

Brake pads on a vehicle become too hot if the brakes are applied for too long. Friction between the brake pads and the wheel discs opposes the motion of the wheel. The force of friction does not work on the brake pads and the wheel disc.

As a result, energy is transferred from the kinetic energy store of the vehicle to the thermal energy store of the brake pads and the wheel discs. This makes them become hot and transfer energy by heating to the thermal energy store of the surrounding air.

25
Q

What is a gravitational potential store, and what does it depend on?

A

When we are above the Earth’s surface we have potential (stored) energy. This is called gravitational potential energy (GPE). This depends upon the mass of the object and its height above the ground.

26
Q

TRUE OF FALSE…

The force you need to lift an object at constant velocity is half the gravitational force on the object.

A

FALSE

The force you need to lift an object at constant velocity is equal to the gravitational force on the object.

27
Q

When an object is moved _______, the energy in its gravitational potential energy stores _________. This increase is _____ to the work done on it by lifting force to overcome the _____________force of the object.

A

upwards
increases
equal
gravitational

28
Q

When an object moves ____, the energy in its gravitational potential energy store _________. This decrease is equal to the work done by the gravitational _____ acting on it.

A

down
decreases
force

29
Q

What is the equation used for the change in an object’s gravitational potential store (including units)?

A

Change in an object’s gravitational potential store (joules, j) =weight (newtons, N) * change of height (metres, m)

30
Q

What is the equation used to find the change of gravitational potential store ∆Ep (joules, J)

A

Change of gravitational potential store ∆Ep (joules, J)= mass, m (kilograms, kg) * gravitational field strength, g(newtons per kilogram, N/Kg) * Change ∆h (meters, m)

31
Q

What is the equation used to find the kinetic energy store of an object?

A

Kinetic energy, Ek (joules, J) = 1/2 * mass (kg) * speed squared (metres per sedond, m/s) squared.

32
Q

What is the equation used to find the elastic potential energy store in an object or a spring?

A

Elastic potential energy, Ee (joules, J) = 1/2 * spring constant,k (newtons per metre, N/m) * extension squared. e squared (metres, m) squared.

33
Q

Explain what useful energy is and what wasted energy is.

Where will wasted energy eventually be transferred?

A

1) Useful energy is energy in the place we want and need.

Wasted energy is energy that is not useful and energy that is transferred by an undesired pathway.

2) Wasted energy will eventually be transferred to the surroundings which will become warmer.

34
Q

What happens to energy as it spreads out (dissipates)?

A

As the energy dissipates it gets less and less useful.

35
Q

How can you work out the efficiency of a device?

A

The efficiency of a device = energy transferred by the device / total energy supplied to the device
(X100)

36
Q

Why do machines waste energy?

A

Machines waste their energy because of friction between their moving parts, air resistance, electrical resistance, and noise.

37
Q

How can machines be made more efficient?

A

Machines can be made more efficient by reducing the energy they waste. For example, lubrication is used to reduce friction between moving parts.

38
Q

What are some uses of everyday electrical appliances?

A

Heating, lighting, using an electric motor and producing sound and visual images.

39
Q

What s an electrical appliance?

A

An electrical appliance is an appliance designed for a particular purpose and should waste as little energy as possible.

40
Q

What is Power?

A

Power is the rate of transfer of energy.

41
Q

How can you work out the power of an appliance?

A

The power of an appliance = Power= energy/time

42
Q

How can you work out the efficiency of an appliance?

A

Efficiency = useful power out / total power in. (X100)

43
Q

How can you work out power wasted by an appliance?

A

Power wasted by an appliance = total power input - useful power output.

Physics (6 decks)

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