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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
Example of vectors
Force, velocity, weight, momentum, acceleration
26
Examples of scalars
Speed, energy, temp, time
27
WHat is displacement
Measures the distance and direction in a straight line from an objects starting point to its finishing point
28
What is velocity
Speed in a stated direction
29
Equation for average speed (m/s)
Distance (m) / time (s)
30
Equation for acceleration (m/s(2))
Change is velocity (m/s) / time taken (s)
31
What’s the equation that links initial and final velocity and acceleration
Final Velocity(2) - initial velocity(2) = 2 x acceleration x distance
32
What is the average speed of walking
1.4 m/s
33
Average speed for running
3 m/s
34
Average car speed (non motorway)
13 m/s
35
What is acceleration
How quickly you’re speeding up, the change in velocity in a certain amount of time
36
Average speed of wind
5-20 m/s
37
Average speed of sound in air
340 m/s
38
Average speed of cycling
5.5 m/s
39
What does the gradient of a distance time graph show
The speed of the object
40
What does the curve getting steeper on a distance time graph mean
Speeding up (increasing gradient)
41
What does the graph levelling off on a distance time graph mean
It’s slowing down (deceasing gradient)
42
How do u work out the gradient/speed from a distance time graph
Change in vertical/change in horizontal
43
What does the gradient mean on a velocity time graph
Acceleration
44
What shows the distance travelled on a velocity time graph
The area under any section of the graph, can split it into rectangles and triangles
45
What is Newton’s first law?
Resultant force is needed to making something start moving, speed up or slow down
46
What is the stopping distance
The sum of the thinking and breaking distance
47
What 6 factors affect stopping distance
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
What is acceleration proportional to
The resultant force
49
What is acceleration inversely proportional to
The mass
50
What does it mean that acceleration is inversely proportional to mass
An object with a larger mass with accelerate less
51
Formula for Newton’s first law
Resultant force (N) = mass(kg) x acceleration (m/s(2))
52
What do safety features in cars increase
Collision time
53
What are crumple zones
Areas at the front of back of a vehicle which crumple up easily in a collision, increasing time taken to stop
54
What’s mass
The amount of matter in an object
55
What is weight
The force acting on an object due to gravity
56
What is force measured in
Newtons
57
What is the centripetal force
The force that keeps something moving in a circle
58
What happens as an object is travelling in an circle at a constant speed
It is constantly changing velocity so it’s accelerating, so it must have a resultant force
59
What different equipment can u use to measure speed
Light gates, stopwatch, rolling tape measure, take a video and look at how far the object travels each frame
60
What is Inertia
The tendency for motion to remain unchanged
61
What does an object interval mass do
Measures how difficult it is to change the velocity of an object
62
What is newtons 3rd law
Reaction forces are equal and opposite
63
What is inertia defined as
The ratio of force over acceleration
64
What is the unit for momentum
Kg m/s
65
What is momentum
The product of the objects mass and velocity
66
What is conservation of momentum
In a closed system the total momentum before an event is equal To The total momentum after
67
What is thinking distance
The distance the car travels in the drivers reaction time
68
What 4 factors affect a drivers reaction time
Tiredness, alcohol, drugs, distractions
69
What is the braking distance
The distance taken to stop once the breaks have been applied
70
What are 2 ways of measuring reaction time
A computer based test, the ruler drop test
71
What is the typical reaction time of someone doing the ruler drop test
0.2-0.6 s
72
What is uniform acceleration
Constant acceleration
73
What is the acceleration in free fall
10 m/s
74
What is conservation of energy
Energy is never created or destroyed
75
What happens where there are energy stores
The total energy of a closed system has no net change
76
What are the 4 ways energy can be transferred between stores
Mechanically, electrically, by heating, by radiation
77
What does energy transferred mechanically mean
A force acting on an object (and doing work) e.g. pushing, stretching, squashing
78
What does energy transferred electrically mean
A charge doing work e.g. Charges moving around a circuit
79
What does energy transferred by heating mean
Energy transfer from a hotter object to a colder object e.g heating a pan on a hob
80
What does energy transferred by radiation mean
Energy transferred by waves e.g. energy from the sun reaching earth by light
81
In a diagram that shows energy transfers what do arrows represent
Transfers
82
In a diagram that shows energy transfers what do boxes represent
The stores
83
What energy transfers are going on in a ball rolling up a slope
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
What energy transfers are going on in a bat hitting a ball
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
What energy transfers are going on in a rock dropped from a cliff
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
What energy transfers are going on in a car slowing down (without braking)
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
What energy transfers are going on in a kettle boiling water
E is transferred electrically from mains to the heating element of the kettle then by heating to the thermal store of the water
88
What is another important principle
Energy is only useful when it is transferred from one store to a useful store
89
When do mechanical processes become wasteful
When they cause a rise in temp so dissipating energy in heating the surroundings
90
What can reduce energy transferred by friction
Lubrication e.g. oil
91
What can reduce rate of energy transfer by heating
Insulation
92
What do thick walls do
Slows the rate of energy transfer
93
What is thermal conductivity
How well a material transfers energy by conduction
94
What things have low thermal conductivity
Gases like air
95
What is a cavity wall
Made up of inner and outer walls with an air gap in the middle - air gap reduces amount of energy transferred by conduction

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