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Physics GCSE > Section 1 - Motion, Forces and Conservation of Energy > Flashcards

Section 1 - Motion, Forces and Conservation of Energy Flashcards

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1
Q

What do vectors have?

A

Magnitude and Direction

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2
Q

Define a vector

A

A quantity with magnitude and direction

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3
Q

Give examples of vector quantities

A

Force, velocity, displacement, weight, accerleation and momentum

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4
Q

What do scalars have?

A

Magnitude

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5
Q

Define a scalar

A

A quantity with magnitude

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6
Q

Give examples of scalar quantites

A

Speed, distance, mass, energy, temperature and time

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7
Q

Define distance

A

How far an object has moved

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8
Q

Define displace

A

The distance an object has moved in a straight line from an object’s starting point to its finishing point

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9
Q

Give one similarity between speed and velocity?

A

Involve how fast an object is going

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10
Q

Define speed

A

How fast an object is

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11
Q

Define velocity

A

How fast an object is in a given direction

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12
Q

What is the equation for speed?

A 
s = d / t
Speed = Distance / Time
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13
Q

Give examples of a scalar and vector quantities

A

Scalar - Speed, distance, mass, energy, temperature and time

Vector - Force, velocity, displacement, weight, accerleation and momentum

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14
Q

A sprinter runs 200m in 25s.

Calculate his average speed

A

200/25=8

8 m/s

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15
Q

How fast is sound in air?

A

340 m/s

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16
Q

What is acceleration?

A

The change in velocity in a certain amount of time

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17
Q

What is the acceleration equation?

A 
a = (v-u) / t
Acceleration = (Final velocity - initial velocity) / Time
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18
Q

True or False? Deceleration has no correlation with acceleration?

A

False, deceleration is simply the opposite (negative) of acceleration

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19
Q

What does uniform acceleration mean?

A

Constant Acceleration

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20
Q

What is the acceleration due to Earth’s gravity?

A

10 m/s^2

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21
Q

What is the uniform acceleration equation?

A

v^2 - u^2 = 2 x a x d

Final Velocity - Inital Velocity = 2 x Acceleration x Distance

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22
Q

A ball is dropped from a height
The acceleration is 10 m/s^2
The speed of the ball just before it hits the ground is 5 m/s
Calculate the height of the ball

A

(5^2-0^2)/2x10=x
(25-0)/20=x
1.25=x

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23
Q

What do distance/time graphs tell you?

A

How far something ha travelled

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24
Q

What does the gradient of a d/t graph tell you?

A

The speed of the object

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25
Q

What do the flat sections of a d/t graph tell you?

A

The object has stopped

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26
Q

What does a curve on a d/t graph tell you?

A

The object is accelerating

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27
Q

What does a steep curve on a d/t graph tell you?

A

The object is speeding up

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28
Q

What does a levelling off curve on a d/t graph tell you?

A

The object is slowing down

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29
Q

How do you find the speed of an object from a d/t graph?

A

Calculate the gradient

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30
Q

True or False? Velocity/Time graphs can have a positive or negative gradient?

A

True

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31
Q

What does the gradient of a v/t graph tell you?

A

The objects acceleration

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32
Q

What do flat sections of v/t graph tell you?

A

The object is at a constant speed

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33
Q

What do uphill sections of a v/t graph tell you?

A

The object is accelerating

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34
Q

What do downhill sections of a v/t graph tell you?

A

The object is decelerating

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35
Q

What do curves on a v/t graph tell you?

A

The object has a changing acceleration

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36
Q

How do you calculate the distance travelled on a v/t graph?

A

By calculating the area under any section of the graph

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37
Q

What is needed to change motion?

A

A force

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38
Q

State newtons first law

A

If the resultant force on a stationary object is zero, the object will remain stationary
If the resultant force on a moving object is zero, it will remain at a constant speed

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39
Q

What is acceleration proportional to?

A

Resultant force

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40
Q

State newtons second law

A

The larger the resultant force, the faster the object accelerates (Force = Mass x Acceleration)

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41
Q

State the equation for resultant force

A 
F = M x A
Force = Mass x Acceleration
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42
Q

Why are large decelerations dangerous?

A

Because in order to stop them it requires a large force (F = M x A)

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43
Q

How can the impact of declerations be reduced?

A

By slowing the object down over a longer time

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44
Q

Give examples of how car safety features reduce the impact of large decelerations?

A

Seat belts stretch
Air bags slow you down gradually
Crumple Zones

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45
Q

What are crumple zones?

A

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

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46
Q

What do the brakes of a vehicle do?

A

They do work on its wheels by transferring energy from the vehicles KE store to thermal

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47
Q

Find the resultant force needed to accelerate an 80kg man on a 10kg bike at 0.25 m/s^2

A
  1. 25x90=22.5

22. 5N

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48
Q

True or False? Weight and Mass are the same?

A

False

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49
Q

Define mass

A

The amount of matter in an object

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50
Q

True or False? Mass is constant anywhere in the universe?

A

True

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51
Q

Define weight

A

The force acting on an object due to gravity

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52
Q

What are the units for mass?

A

Grams

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53
Q

What are the units for weight?

A

Newtons

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54
Q

What is the centre of mass for an object?

A

The point at which you assume the whole mass is concentrated

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55
Q

What does weight depend on?

A

Mass and Graviational FIeld Strength

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56
Q

What is the equation for weight?

A 
W = M x GFS
Weight = Mass x Graviational Field Strength
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57
Q

What is constantly changing with circular motion?

A

Velocity and Acceleration

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58
Q

With centripetal forces, where does the force act?

A

Towards the centre of the circle

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59
Q

Calculate the weight in newtons of a 25kg mass on the Earth?

A

25x10=250

250N

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60
Q

Calculate the weight in newtons of a 25kg mass on the Moon?

A

25x1.6=40

40N

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61
Q

When investigating the motion of a trolley on a ramp, what must you measure before you do the practical?

A

The mass of the trolley
The unit masses
The hanging hook
The length of the piece of card

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62
Q

When investigating the motion of a trolley on a ramp, what do you set the height as?

A

Just as the trolley starts to move

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63
Q

When investigating the motion of a trolley on a ramp, what is the goal of the light gates?

A

To record the time and speed of the trolleys so they can be used to calculate the acceleration

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64
Q

When investigating the motion of a trolley on a ramp, what results should you expect?

A

As the force increases, the acceleration increases
Which means the force and acceleration are proportional
As the mass increases, the acceleration decreases
Which means the mass and acceleration are inversely proportional

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65
Q

Why are light gates the best option?

A

Because they get rid of human error caused by reaction times

66
Q

How could you find someones walking speed

A

Measure the distance and stopwatch it

Then use S = D / T

67
Q

Define inertia

A

The tendency for motion to remain unchanged

68
Q

What is an objects inertial mass?

A

The measurement of how difficult it is to change the velocity of an object

69
Q

What is the equation for inertial mass?

A 
M = F / A
Mass = Force / Acceleration
70
Q

What is inertial mass the ratio of?

A

Force over acceleration

71
Q

What is newton’s third law?

A

When two objects interact, the forces they exert on each other are equal and opposite

72
Q

A full shopping trolley and an empty one are moving at the same speed
Explain why it is easier to stop the empty trolley than the full trolley over the same amount of time?

A

An object with less mass will have less inertial mass so less force will be needed to stop it

73
Q

What kind of objects have momentum?

A

All moving objects

74
Q

Define momentum

A

The product of an objects mass and velocity

75
Q

What is the equation for momentum?

A 
P = M x V
Momentum = Mass x Velocity
76
Q

What kind of quantity is momentum?

A

A vector quantity

77
Q

How does an object gain momentum?

A

Increase the mass or increase its velocity

78
Q

True or False? In a closed system, the total momentum before an event and after is the same?

A

True

79
Q

What is the equation linking momentum before and momentum after?

A

Total Momentum Before = Total Momentum After

80
Q

What is a closed system?

A

A system with no external forces acting

81
Q

Calculate the momentum of a 60kg woman running at 3m/s?

A

60x3=180

180 kg m/s

82
Q

Describe how momentum is conserved by a gun recoiling as it shoots a bullet?

A

Before the gun is fired the total momentum is zero
Once the bullet leaves the gun it has momentum in one direction
The gun moves backwards and has an equal but opposite momentum to the bullet
This means that the total momentum after the bullet has been fired is still zero. Meaning momentum has been conserved

83
Q

What causes changes in momentum?

A

Forces

84
Q

What is the change in momentum equation?

A 
F = (mv-mu) / t
Force = Change in momentum / Time
85
Q

What will the force be for a big change in momentum?

A

A big force

86
Q

Which of newton’s law is shown by conservation of momentum?

A

Newton’s Third Law

87
Q

Calculate the force a tennis racket needs to apply to a 58g tennis ball to accelerate it from rest to 34 m/s in 11.6ms

A

(0.58(34)-0.58(0)) / 0.0116 = 170

170N

88
Q

What is the stopping distance equation?

A

Stopping Distance = Thinking Distance + Braking Distance

89
Q

What is the thinking distance?

A

The distance the car travels in the driver’s reaction time

90
Q

What periods is part of the drivers reaction time?

A

Noticing the hazard and applying the brakes

91
Q

What factors affect your thinking distance?

A

The drivers reaction time and speed

92
Q

What increases your reaction time?

A

Tiredness, alcohol, drugs and distractions

93
Q

What is the braking distance?

A

The distance taken to stop once the brakes have been applied

94
Q

What factors affect your braking distance?

A

Road conditions, mass of the car, speed of the car and the condition of the brakes

95
Q

True or False? Everyones reaction time is the same?

A

False, everyones reaction time is different

96
Q

Drivers on long journeys should take regular breaks

Explain why, in terms of stopping distance?

A

If you’re tired your reaction time is likely to be longer which would increase thinking distance and so stopping distance. This would make an accident more likely if you needed to brake suddenly

97
Q

What must drivers do to avoid an accident?

A

Leave eough space in front so they could stop safely

98
Q

Why are speed limits really important?

A

Because speed affects stopping distance massively

99
Q

True or False? As speed increases, thinking distance increases at the same rate?

A

True, because driver’s reaction time stays fairly constant but the higher the speed, the further you go in that time

100
Q

What type of relationship do speed and braking distance have?

A

A squared relationship

101
Q

What must brakes do to stop a car?

A

The brakes must transfer the equivalent kinetic energy of the car

102
Q

What is the equation linking KE and Work Done?

A

1/2 x m x v^2 = F x d

1/2 x Mass x Velocity^2 = Force x Distance

103
Q

Estimate the size of the force needed to stop a lorry travelling at 16 m/s within 50m

A

1/2mv^2=Fd
mv^2+2d=F
30,000 x 16^2 + (2x50) = 76,800
80,000 N

104
Q

State all the energy stores

A 
Kinetic
Thermal
Graviational Potential
Elastic Potential
Electrostatic
Nuclear
Chemical
105
Q

How many energy stores are there?

A

8

106
Q

What type of object will have kinetic energy?

A

A moving object

107
Q

What does an objects kinetic energy depend on?

A

It’s velocity and mass

108
Q

What is the kinetic energy equation?

A

Kinetic Energy = 0.5 x Mass x Velocity²

J = 0.5 x Kg x (m/s)²

109
Q

If you double the mass what happens to the KE of the object?

A

It doubles as well

110
Q

If you double the speed what happens to the KE of the object?

A

It increases by a factor of four as there is a squared relationship

111
Q

A car of mass 1450 kg is travelling at 28 m/s

Calculate the energy in it’s kinetic energy store, giving your answer to 2 s.f.?

A 
KE = 0.5 x M x V²
KE = 0.5 x 1450 x 28²
KE = 570,000 J (2 SF)
112
Q

An Object at a Height has Energy in its ______________________________

A

An Object at a Height has Energy in its Graviational Potential Energy Store

113
Q

What is the graviational potential energy equation?

A

Graviational Potential Energy = Mass x Gravity x Height

J = kg x N/kg x m

114
Q

A 2kg object is dropped from a height of 10m.

Calculate the speed of the object after it has fallen 5m, assuming there is no air resistance

A 
GPE = m x g x h
GPE = 2 x 10 x 5
GPE = 100 J

100 = 0.5 x 2 x V²
100 = V²
10 = V
10 m/s

115
Q

What is conservation of energy?

A

The principle that “Energy can be stored, transferred between stores and dissipated but it can never be created or destroyed. The total energy of a closed system has no net change”

116
Q

List ways energy can be transferred

A

Mechanically
Electrically
Radiation
Heating

117
Q

How can energy be transferred mechanically?

A

By a force doing work

118
Q

How can energy be transferred electrically?

A

By a charge doing work

119
Q

How can energy be transferred by heating?

A

Energy transferred from a hotter object to a colder object

120
Q

How can energy be transferred by radiation?

A

Energy transferred by waves

121
Q

Describe the energy transfers that occur when a piece of wood is burnt

A

Chemical energy store in wood is transferred by heating to the thermal energy stores of the surroundings
The rest of the energy is transferred away by light waves.

122
Q

When is energy useful?

A

When it is transferred from one store to a useful store

123
Q

Total Energy Input = ______________________________

A

Total Energy Input = Useful Energy Output + Wasted Energy

124
Q

What is the efficiency equation?

A

Efficiency = Useful Energy / Total Energy

125
Q

A toaster transfers 216,000 of energy electrically from the mains
84,000 J of energy is transferred to the bread’s thermal energy store
Calculate the efficiency of the toaster

A 
Efficiency = Useful / Total
Efficiency = 84,000  / 216,000
Efficiency = 39%
126
Q

An electrical device wastes 420 J of energy when it has an input energy of 500J
Calculate the efficiency of the device as a percentage

A

500 - 420 = 80
Efficiency = Useful / Total
Efficiency = 80 / 500
Efficiency = 16%

127
Q

Give methods of reducing energy loss

A

Lubrication

Thermal Insulation

128
Q

How does lubrication reduce energy loss?

A

By reducing friction

129
Q

How does insulation reduce energy loss?

A

By reducing the rate of energy loss to thermal energy

130
Q

How are houses insulated?

A

Cavity walls
Thick walls
Double glazing windows
Foil behind radiators

131
Q

What is conduction?

A

When particles transfer energy through an object

132
Q

What is thermal conductivity?

A

The description of how well an object transfers energy by conduction

133
Q

Suggest one way to improve the efficiency of an electric motor

A

Lubrication of moving parts

134
Q

Give examples of renewable energy resources?

A 
Bio-fuels
Wind
Solar
Hydro-electricity
Tidal
135
Q

State two renewable energy sources

A 
Two of:
Bio-fuels
Wind
Solar
Hydro-electricity
Tidal
136
Q

The government is considering closing down a traditional coal-fired power station
Explain the benefits and disadvantages of replacing the power station with a wind farm

A

Benefits are cheaper fuel, better for the environment and low running costs
Disadvantages are high cost to destroy and build turbines, unreliable, takes up space and spoils the view

137
Q

Give two reasons we currently do not use more renewable energy resources in the UK

A

Expensive

Unreliable

138
Q

What is the difference between a scalar and vector quantity? Give two examples of each

A

Scalar are quantities with magnitude but no direction, whilst vectors are quantites with magnitude and direction

139
Q

Estimate typical speeds for walking

A

1.5 m/s

140
Q

Estimate typical speeds for running

A

3 m/s

141
Q

Estimate typical speeds for a car in a built-up area

A

13 m/s

142
Q

Define accerleration in terms of velocity and time

A

The rate at which velocity changes over time

143
Q

What does gradient represent for a d/t graph?

A

The speed of the object

144
Q

What does a gradient represent for a v/t graph?

A

The acceleration of the object

145
Q

How would you find the distance travelled by an object from its v/t graph?

A

By calculating the area underneath the graph

146
Q

Explain why cars have safety features to reduce the decelerations experienced by passengers

A

Because without the time before collision increase, the force would be greater causing more injuries

147
Q

What is the formula for calculating the weight of an object?

A

Weight = Mass x Graviational Field Strength

148
Q

Explain why there must be a force acting to produce circular motion?

A

Because direction is forever changing in circular motion meaning there must be a force

149
Q

What is the name for circular motion?

A

Centripetal

150
Q

Describe an experiment to investigate Newton’s Second Law of Motion?

A

Pull trolley down hill
Experiment with different masses
Time to calculate speed

151
Q

What is inertia?

A

The tendency for motion to remain unchanged

152
Q

What is newton’s third law of motion?

A

For every action there is an equal yet opposite reaction

153
Q

State the formula used to calculate momentum?

A

Momentum = Mass x Velocity

kg m/s = kg x m/s

154
Q

Explain the link between Newton’s Third Law and conservation of momentum

A

Both involve the theorem that states whenever objects collide they share magnitude (forces or momentum)

155
Q

What is meant by a person’s reaction time?

A

How quickly a person can respond to a stimulus

156
Q

State two factors that can affect the thinking distance for a stopping car

A

Speed

Reaction time

157
Q

State four factors that can affect the braking distance of a stopping car

A

Condition of the brakes
Mass of the car
Speed of the car
Conditions of the road

158
Q

What is meant by the dissipation of energy?

A

The transfer of energy to wasted energy stores

159
Q

Describe the energy transfers when a ball is rolled up a slope

A

Kinetic Energy -> Graviational Potential Energy & Sound Energy

160
Q

Describe the energy transfer when a hair dryer is switched on

A

Electrical Energy -> Thermal Energy & Sound Energy

Physics GCSE (8 decks)

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