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GCSE WJEC Physics > Topic 11 - Work and Energy > Flashcards

Topic 11 - Work and Energy Flashcards

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1
Q

What is a system?

A

An object or group of objects.

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2
Q

What are the different ways energy can be stored in a system?

A

Kinetic store, gravitational potential store, chemical store, elastic potential store, nuclear store and internal store

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3
Q

What is a kinetic store?

A

The energy stored by an object’s movement.

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4
Q

What is a gravitational potential store?

A

The energy stored in objects raised above the Earth’s surface, due to the Earth’s gravitational field.

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5
Q

What is a chemical store?

A

The energy stored by the chemical bonds between atoms.

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6
Q

What is an elastic potential store?

A

The energy stored when an object is being stretched, compressed or squashed.

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7
Q

What is a nuclear store?

A

The energy stored in the nucleus of an atom that can be released by radioactive decay.

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8
Q

What is an internal store?

A

Sum of the kinetic energy stored in the particles of an object and the chemical energy stored in chemical bonds between particles in the object.

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9
Q

What is the equation for kinetic energy?

A

1/2 x mass x velocity2

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10
Q

What is the equation for the change in GPE?

A

Mass x gravitational field strength x change in height

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11
Q

What is energy measured in?

A

Joules

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12
Q

What is the equation for elastic potential energy?

A

1/2 x spring constant x extension2

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13
Q

What is the spring constant measured in?

A

N/m

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14
Q

What is the extension measured in?

A

Metres

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15
Q

What is the conservation of energy?

A

Energy cannot be created or destroyed, only transformed

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16
Q

How can energy be transformed?

A

Electrical work, heating, waves, mechanical work

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17
Q

What is electrical work?

A

When an electrical current transfers energy from one object to another.

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18
Q

How does heating transform energy?

A

Heating an object increases its internal energy.

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19
Q

How do waves transform energy?

A

Light and other types of waves can transfer energy from one object to another.

20
Q

What is mechanical work?

A

When energy transferred from one object to another via a force.

21
Q

What is the equation for work done?

A

Force x distance (moved along the line of action of the force)

22
Q

How can more work be done?

A

Applying the same force over a longer distance, apply a larger force for the same distance.

23
Q

What is work?

A

Total change in energy of/energy transferred to an object.

24
Q

What is on the x-axis of an extension-load graph?

A

The extension of the spring

25
Q

What is on the y-axis of an extension-load graph?

A

The force acting on the spring

26
Q

What is a limit of proportionality?

A

When an object will not return to its original length when the force is removed.

27
Q

What is extension directly proportional to?

A

The force applied

28
Q

What happens if a spring is over-stretched?

A

It will not return to its original length

29
Q

What relationship do spring constant and spring stiffness have?

A

The higher the spring constant, the stiffer the spring.

30
Q

What is Hooke’s Law?

A

Force = spring constant x extension

31
Q

Which letter is used to represent extension?

A

e or x

32
Q

Which letter is used to represent spring constant?

A

k

33
Q

Investigating Hooke’s Law 1

A

First, measure the original length of the spring.

34
Q

Investigating Hooke’s Law 2

A

Next, hang different masses on the spring and measure the length of the spring in each case.

35
Q

Investigating Hooke’s Law 3

A

Adding masses to the spring increases the downwards force as each mass has weight.

36
Q

Investigating Hooke’s Law 4

A

The extension of the spring equals the length with masses minus the original length.

37
Q

Investigating Hooke’s Law 5

A

Plot a graph with extension of the spring on the x axis and force on the y axis.

38
Q

How can the extension of the spring be worked out in an investigation?

A

Length of the loaded spring − natural length of the spring

39
Q

What apparatus is needed to investigate Hooke’s Law?

A

A spring, a ruler and a known mass

40
Q

What happens when a spring is compressed?

A

Elastic potential energy is stored in the spring (so long as a spring isn’t inelastically deformed).

41
Q

What is the elastic potential energy stored in a stretched spring equal to?

A

The work done when stretching it

42
Q

What does the area under a force-extension graph show?

A

The elastic potential energy stored in a stretched spring

43
Q

What is the equation for percentage efficiency?

A

Useful energy output/total energy output x 100

44
Q

How could the energy efficiency of a toy car be increased?

A

Improve aerodynamics and lubricate the track

45
Q

Why does lubrication increase energy efficiency?

A

It reduces frictional forces, reducing dissipated energy

46
Q

Why does aerodynamicising the car increase energy efficiency?

A

It reduces the effects of air resistance.

GCSE WJEC Physics (3 decks)

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