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A level Physics > Unit 1.4 - Energy Concepts > Flashcards

Unit 1.4 - Energy Concepts Flashcards

1
Q

Work definition

A

The transfer of energy as an object moves (it displaces it)

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2
Q

The transfer of energy as an object moves

A

Work

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3
Q

Work done formula

A

Fx = cos(O)

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4
Q

Fx = cos(O)

A

Work done

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5
Q

Work unit

A

J

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6
Q

Which is the only component that contributes to work?

A

The x component

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7
Q

What is f in the work done formula?

A

Force applied

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8
Q

What is x in the work done formula?

A

Displacement

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9
Q

What is cos(O) in the work done formula?

A

The angle between f and x

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10
Q

What changes when work is done?

A

Kinetic enegry

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11
Q

When does kinetic energy change?

A

When work is done

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12
Q

What is the change in kinetic energy if work is done against the motion of an object?

A

Negative change in kinetic energy

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13
Q

What is the change in kinetic energy if work is done with the motion of an object?

A

Positive change in kinetic energy

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14
Q

If there’s a negative change in kinetic energy, describe the work done

A

Against the motion of an object

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15
Q

If there’s a positive change in kinetic energy, describe the work done

A

Work done with the motion

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16
Q

Energy definition

A

The ability to do work

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17
Q

The ability to do work

A

Energy

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18
Q

Energy unit

A

J

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19
Q

Which two concepts in physics have cylindrical definitions?

A

Work and energy

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20
Q

Are work and energy scalar of vector? Why?

A

Scalar, as they have no direction

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21
Q

Do work and energy have direction? Why?

A

No, as they’re scalar measurements

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22
Q

As work and energy have no direction, what can they be instead?

A

(+) or (-)

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23
Q

Kinetic energy

A

Energy of motion

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24
Q

Energy of motion

A

Kinetic energy

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25
Q

Energy of location

A

Potential energy

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26
Q

Potential energy

A

Energy of location

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27
Q

Kinetic energy formula

A

1/2 mv^2

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28
Q

1/2mv^2 formula

A

Kinetic energy

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29
Q

What is m in the kinetic energy formula?

A

Mass (kg)

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30
Q

What is v in the kinetic energy formula?

A

Velocity

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31
Q

What is the work energy theorem (worded)?

A

Net work = final KE - initial KE

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32
Q

Work energy theorem equation

A

Fx = 1/2mv^2 - 1/2mu^2

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33
Q

What is Fx = 1/2mv^2 - 1/2mu^2?

A

Work energy theorem

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34
Q

If the net work is negative, what does this mean?

A

Work done BY the system

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35
Q

Negative net work

A

Work done BY the system

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36
Q

If the net work it positive, what does this mean?

A

Work done ON the system

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37
Q

Positive net work

A

Work done ON the system

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38
Q

Potential energy formula

A

E = mgΔh

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39
Q

E = mgΔh

A

Potential energy

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40
Q

If an object is higher, how does its potential energy change?

A

More potential energy

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41
Q

What changes for an object when it’s higher up?

A

Its potential energy, which is higher

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42
Q

When is ALL of the potential energy converted into kinetic energy when an object travels down something (e.g - a ramp)?

A

With zero resistive forces

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43
Q

With zero resistive forces when an object travels down something (e.g - a ramp), what happens to the energy?

A

All of the potential energy is converted into kinetic energy

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44
Q

What does the fact that, with zero resistive forces, all of the potential energy is transferred into kinetic energy allow us to do?

A

The velocity at the end of the ramp

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45
Q

Under which conditions can we calculate the velocity at the end of a ramp?

A

When there’s no resistive forces so all of the potential energy is transferred into kinetic energy

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46
Q

Give 2 examples of resistive forces

A

Friction and air resistance

47
Q

What are friction and air resistance examples of?

A

Resistive forces

48
Q

What do resistive forces cause in terms of energy conversation?

A

Causes some of the initial potential energy to be converted to thermal energy

49
Q

Under which conditions is potential energy converted into thermal energy when an object moves down something (e.g - a ramp)?

A

With resistive forces

50
Q

What is thermal energy?

A

The label for the work done against the resistive forces

51
Q

What is the label for the work done against the resistive forces?

A

Thermal energy

52
Q

Describe the final velocity of an object when resistive forces act?

A

Lower

53
Q

Under which conditions is the final velocity of an object lower?

A

With resistive forces

54
Q

How can we calculate the work done against resistive forces?

A

Difference between initial PE and final KE

55
Q

What does the difference between intial PE and final KE calculate?

A

The work done against resistive forces

56
Q

How do we calculate the mean resistive force acting on a body?

A
  1. Calculate the initial potential energy
  2. Calculate the final kinetic energy
  3. Calculate the work done against the resistive force (the difference between these two)
  4. Mean force = work/displacement (W=fx rearranged)
57
Q

Mean force

A

Work done
——————
Displacement

(W = fx rearranged)

58
Q

Elastic potential energy definition

A

The energy stored in a material under tension (or compression)

59
Q

The energy stored in a material under tension (or compression)

A

Elastic potential energy

60
Q

What does elastic potential energy apply to?

A

Any elastic material (often a spring)

61
Q

What type of energy occurs to elastic materials?

A

Elastic potential energy

62
Q

Elastic potential energy equation

A

E=1/2kx^2

63
Q

E=1/2kx^2

A

Elastic potential energy

64
Q

What’s ‘k’ in the elastic potential energy equation?

A

Spring constant (Nm-1)

65
Q

Spring constant unit

A

Nm-1

66
Q

What’s ‘x’ in the elastic potential energy equation?

A

Change in length (extension)

67
Q

Spring constant

A

‘k’ in the elastic potential energy formula
The amount the material increases in length per unit force

68
Q

The amount a material increases in length per unit force

A

Spring constant (Nm-1)

69
Q

Alternative equation for elastic potential energy

A

W = 1/2fx

70
Q

F=kx

A

Hooke’s law

71
Q

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

A

Work done

72
Q

What’s the gradient on a force-extension graph for a spring?

A

k (spring constant) (Nm-1)

73
Q

How do you calculate the energy in a spring using a force-extension graph?

A

Force x distance in this direction
=area under the graph
W = 1/2fx

74
Q

W = 1/2fx

A

Energy in a spring (work done) - alternative equation

(Only use it on spring questions!)

75
Q

Work done = elastic potential energy stored in the spring
…Provided what?

A

Provided that Inelastic deformation hasn’t occurred

76
Q

If Inelastic deformation occurred, which rule would not be accurate anymore with springs?

A

That work done = elastic potential energy stored in the spring

77
Q

Power

A

The rate of energy transfer

78
Q

The rate of energy transfer

A

Power

79
Q

Describe power

A

The amount of energy that is transferred per second

80
Q

What is the amount of energy that is transferred per second known as?

A

Power

81
Q

Unit of power

A

W

82
Q

W is the unit of…

A

Power

83
Q

What IS 1 W?

A

1Js-1

84
Q

1Js-1

A

1W

85
Q

Equation for power

A

P = W/t = ΔE/t

86
Q

P = W/t = ΔE/t

A

Equation for power

87
Q

What do we do for ΔE in the power equation?

A

Input necessary energy equation

88
Q

What is W in the power equation?

A

Work done

89
Q

What is ΔE in the power equation?

A

Change in energy (J)

90
Q

What would a high rate of transferring energy give us?

A

High power

91
Q

What would give us a high power?

A

A high rate of transferring energy

92
Q

What would a low rate of transferring energy give us?

A

A low power

93
Q

What would give us a low power?

A

A low rate of transferring energy

94
Q

What do resistive forces such as air resistance and friction cause energy to be lost as?

A

Cause energy to be lost as internal energy in the atoms in the objects and surroundings

95
Q

When is energy lost as internal energy and in what?

A

Resistive forces (e.g - friction, air resistance), in the atoms in the objects and surroundings

96
Q

Efficiency equation

A

Useful energy transfer
——————————— x100%
Total energy input

97
Q

What causes energy to be transferred from a system and reduce the overall efficiency of the system?

A

Dissipating forces (e.g - friction or drag)

98
Q

Draw an energy transfer diagram from potential to kinetic energy

A

(Check notes)

99
Q

What’s 1 Watt in Joules?

A

1W = 1Js-1

100
Q

How can an absolute uncertainty be calculated?

A

Range
———
2

101
Q

What is work done?

A

Force in the DIRECTION of travel

102
Q

Which height do we use for gravitational potential energy?

A

Directly upwards - if we’re given an angled slope, we must calculate the change in height directly upwards from it

103
Q

What happens in terms of work when kinetic energy is transferred into gravitational potential energy?

A

Work is done against gravity

104
Q

When is work done against gravity?

A

When kinetic energy is transferred into gravitational potential energy

105
Q

What must we always refer to when transferring between types of energy?

A

Work done

106
Q

When is work done?

A

During the transfer of energy

107
Q

How is kinetic energy lost to air resistance?

A

Object hits air molecules
Looses kinetic energy
Gains heat energy

108
Q

How is heat energy gained?

A

When an object loses kinetic energy when hitting air molecules (air resistance)

109
Q

Describe the force in the work done equation

A

Force in DIRECTION OF TRAVEL

110
Q

Spring constant gradient

A

Nm^-1

111
Q

Work done definition

A

Force x distance in direction of force

112
Q

Elastic potential energy in a slack rope

A

0J

113
Q

Spring constant

A

Tension per unit extension

A level Physics (29 decks)

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