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Physics > 1) Conservation Of Energy > Flashcards

1) Conservation Of Energy Flashcards

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1
Q

What are the different energy stores?

A
  • kinetic
  • thermal
  • chemical
  • elastic potential
  • gravitational potential
  • magnetic
  • nuclear
  • electrostatic
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2
Q

What is a kinetic energy store?

A

When an object is moving, it has energy in its kinetic energy store, energy is transferred to the store if the object speeds up, and away if it slows down

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3
Q

What does the kinetic energy store depend on?

A

Speed and mass

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4
Q

What happens to the kinetic energy store if the mass doubles?

A

The kinetic energy store doubles

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5
Q

What happens to the kinetic energy store if the speed doubles?

A

The energy in the kinetic energy store quadruples (increases by the factor of 4)

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6
Q

What is the equation for kinetic energy?

A

KE = O.5 x mass x (speed)2

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7
Q

What is the equation for GPE?

A

GPE = M x GFS x change in vertical height

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8
Q

What does the conservation of energy mean?

A

It means that energy is never created, nor destroyed, only transferred or stored

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9
Q

What are the main transfers of energy and what do they mean?

A
  • mechanically=a force acting on an object e.g. pushing, stretching
  • electrically=a charge doing work e.g. charges moving round a circuit
  • by heating=energy transferred from a hotter object to a colder one
  • by radiation=energy transferred by waves e.g energy from the sun reaching the earth by light
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10
Q

What is the equation for the total energy input?

A

Total energy input = useful energy output + wasted energy

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11
Q

What is the equation for efficiency?

A

Efficiency = useful energy transferred by device(j) / total energy supplied to device(j)

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12
Q

Fact about efficiency

A

Some energy is always wasted, the efficiency can never be equal to or higher than 1(100%)

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13
Q

What are the two main ways to reduce wasted energy?

A

Lubrication-liquids like oil coat the object and reduce friction
Thermal insulation-reduces the rate of energy transferred by heating(conduction)

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14
Q

What type of diagrams show the efficiency of something?

A

Sankey diagrams

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15
Q

What are non-renewable resources and some examples

A

Non-renewable means they will eventually run out.

Examples: fossil fuels and nuclear energy

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16
Q

Advantages of fossil fuels

A
  • They are reliable
  • fossil fuel power plants are relatively cheap to build&run
  • they can respond quickly to changes in energy demand
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17
Q

Disadvantages of fossil fuels

A
  • they’re slowly running out

- they create environmental problems: global warming, acid rain

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18
Q

Advantages of nuclear power

A
  • it’s clean apart from the waste

- it is reliable

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19
Q

Disadvantages of nuclear power

A
  • the nuclear waste is very dangerous and difficult to dispose of
  • nuclear power plants are pretty costly to build and safely decommission
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20
Q

What does renewable resources mean, and examples

A

Renewable energy resources will never run out.

Examples: biomass, wind, solar, hydro-electricity, tidal, wave, geothermic power

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21
Q

Advantages of biomass

A

Renewable
Carbon neutral
Fairly reliable

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22
Q

Disadvantages of biomass

A

Very costly
Could not be enough space/water for food crops
Some forests have been destroyed to create space for biomass crops to be grown-destroys habitats

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23
Q

What do vector quantities have

A

Magnitude and direction

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24
Q

What do scalar quantities have

A

Magnitude but no direction

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25
Q

Example of vectors

A

Force, velocity, weight, momentum, acceleration

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26
Q

Examples of scalars

A

Speed, energy, temp, time

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27
Q

WHat is displacement

A

Measures the distance and direction in a straight line from an objects starting point to its finishing point

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28
Q

What is velocity

A

Speed in a stated direction

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29
Q

Equation for average speed (m/s)

A

Distance (m) / time (s)

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30
Q

Equation for acceleration (m/s(2))

A

Change is velocity (m/s) / time taken (s)

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31
Q

What’s the equation that links initial and final velocity and acceleration

A

Final Velocity(2) - initial velocity(2) = 2 x acceleration x distance

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32
Q

What is the average speed of walking

A

1.4 m/s

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33
Q

Average speed for running

A

3 m/s

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34
Q

Average car speed (non motorway)

A

13 m/s

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35
Q

What is acceleration

A

How quickly you’re speeding up, the change in velocity in a certain amount of time

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36
Q

Average speed of wind

A

5-20 m/s

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37
Q

Average speed of sound in air

A

340 m/s

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38
Q

Average speed of cycling

A

5.5 m/s

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39
Q

What does the gradient of a distance time graph show

A

The speed of the object

40
Q

What does the curve getting steeper on a distance time graph mean

A

Speeding up (increasing gradient)

41
Q

What does the graph levelling off on a distance time graph mean

A

It’s slowing down (deceasing gradient)

42
Q

How do u work out the gradient/speed from a distance time graph

A

Change in vertical/change in horizontal

43
Q

What does the gradient mean on a velocity time graph

A

Acceleration

44
Q

What shows the distance travelled on a velocity time graph

A

The area under any section of the graph, can split it into rectangles and triangles

45
Q

What is Newton’s first law?

A

Resultant force is needed to making something start moving, speed up or slow down

46
Q

What is the stopping distance

A

The sum of the thinking and breaking distance

47
Q

What 6 factors affect stopping distance

A

Mass of the vehicle, sped of the vehicle, drivers reaction time, state of the vehicles breaks, state of the road, amount of friction between the tyre and the road surface

48
Q

What is acceleration proportional to

A

The resultant force

49
Q

What is acceleration inversely proportional to

A

The mass

50
Q

What does it mean that acceleration is inversely proportional to mass

A

An object with a larger mass with accelerate less

51
Q

Formula for Newton’s first law

A

Resultant force (N) = mass(kg) x acceleration (m/s(2))

52
Q

What do safety features in cars increase

A

Collision time

53
Q

What are crumple zones

A

Areas at the front of back of a vehicle which crumple up easily in a collision, increasing time taken to stop

54
Q

What’s mass

A

The amount of matter in an object

55
Q

What is weight

A

The force acting on an object due to gravity

56
Q

What is force measured in

A

Newtons

57
Q

What is the centripetal force

A

The force that keeps something moving in a circle

58
Q

What happens as an object is travelling in an circle at a constant speed

A

It is constantly changing velocity so it’s accelerating, so it must have a resultant force

59
Q

What different equipment can u use to measure speed

A

Light gates, stopwatch, rolling tape measure, take a video and look at how far the object travels each frame

60
Q

What is Inertia

A

The tendency for motion to remain unchanged

61
Q

What does an object interval mass do

A

Measures how difficult it is to change the velocity of an object

62
Q

What is newtons 3rd law

A

Reaction forces are equal and opposite

63
Q

What is inertia defined as

A

The ratio of force over acceleration

64
Q

What is the unit for momentum

A

Kg m/s

65
Q

What is momentum

A

The product of the objects mass and velocity

66
Q

What is conservation of momentum

A

In a closed system the total momentum before an event is equal
To The total momentum after

67
Q

What is thinking distance

A

The distance the car travels in the drivers reaction time

68
Q

What 4 factors affect a drivers reaction time

A

Tiredness, alcohol, drugs, distractions

69
Q

What is the braking distance

A

The distance taken to stop once the breaks have been applied

70
Q

What are 2 ways of measuring reaction time

A

A computer based test, the ruler drop test

71
Q

What is the typical reaction time of someone doing the ruler drop test

A

0.2-0.6 s

72
Q

What is uniform acceleration

A

Constant acceleration

73
Q

What is the acceleration in free fall

A

10 m/s

74
Q

What is conservation of energy

A

Energy is never created or destroyed

75
Q

What happens where there are energy stores

A

The total energy of a closed system has no net change

76
Q

What are the 4 ways energy can be transferred between stores

A

Mechanically, electrically, by heating, by radiation

77
Q

What does energy transferred mechanically mean

A

A force acting on an object (and doing work) e.g. pushing, stretching, squashing

78
Q

What does energy transferred electrically mean

A

A charge doing work e.g. Charges moving around a circuit

79
Q

What does energy transferred by heating mean

A

Energy transfer from a hotter object to a colder object e.g heating a pan on a hob

80
Q

What does energy transferred by radiation mean

A

Energy transferred by waves e.g. energy from the sun reaching earth by light

81
Q

In a diagram that shows energy transfers what do arrows represent

A

Transfers

82
Q

In a diagram that shows energy transfers what do boxes represent

A

The stores

83
Q

What energy transfers are going on in a ball rolling up a slope

A

Ball does work against the gravitational force, so energy is transferred mechanically from the KE store of the ball to its gravitational potential energy store

84
Q

What energy transfers are going on in a bat hitting a ball

A

The bat has energy in its KE store, some of this is transferred mechanically to the balls KE store. Some is also transferred mechanically to the thermal store of the bat and ball(and to surroundings by heating) rest is carried away by sound

85
Q

What energy transfers are going on in a rock dropped from a cliff

A

Assuming there’s no air resistance, gravity does work on the rock so the rock constantly accelerates towards the ground, e transferred mechanically from the rocks GPE store to its KE stor

86
Q

What energy transfers are going on in a car slowing down (without braking)

A

E in the KE store of thr car is transferred mechanically (due to friction between the tyres and the road) and then by heating, to the thermal store of the car and road

87
Q

What energy transfers are going on in a kettle boiling water

A

E is transferred electrically from mains to the heating element of the kettle then by heating to the thermal store of the water

88
Q

What is another important principle

A

Energy is only useful when it is transferred from one store to a useful store

89
Q

When do mechanical processes become wasteful

A

When they cause a rise in temp so dissipating energy in heating the surroundings

90
Q

What can reduce energy transferred by friction

A

Lubrication e.g. oil

91
Q

What can reduce rate of energy transfer by heating

A

Insulation

92
Q

What do thick walls do

A

Slows the rate of energy transfer

93
Q

What is thermal conductivity

A

How well a material transfers energy by conduction

94
Q

What things have low thermal conductivity

A

Gases like air

95
Q

What is a cavity wall

A

Made up of inner and outer walls with an air gap in the middle - air gap reduces amount of energy transferred by conduction

Physics (7 decks)

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