Combined Physics Foundation 6.5 Flashcards

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1
Q

What are physical quantities with only magnitude (and no direction)?

A

Scalar quantities

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2
Q

What are physical quantities with magnitude and direction?

A

Vector quantities

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3
Q

Give some examples of scalar quantities

A
  • Speed
  • Distance
  • Mass
  • Temperature
  • Time
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4
Q

Give some examples of vector quantities

A
  • Force
  • Velocity
  • Displacement
  • Acceleration
  • Momentum
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5
Q

What does the arrow for a vector quantity show?

A

The length of the arrow shows the magnitude and the direction of the arrow shows the direction of the vector quantity

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6
Q

What is a force?

A

A push or pull acting on an object due to the interaction with another object

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7
Q

What are forces between objects classified as?

A

Contact or non-contact forces

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8
Q

Describe contact forces

A

Objects which are physically touching

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9
Q

Describe non-contact forces

A

Objects are physically separated

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10
Q

Give some examples of contact forces

A
  • Friction
  • Air resistance
  • Tension
  • Normal contact force
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11
Q

Give some examples of non-contact forces

A
  • Gravitational force
  • Electrostatic force
  • Magnetic force
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12
Q

What type of quantity is force?

A

A vector quantity

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13
Q

What is weight?

A

The force acting on an object due to gravity

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14
Q

What cause the force of gravity close to the Earth?

A

The gravitational field around the Earth

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15
Q

If mass it constant, what can affect the weight of an object?

A

The gravitational field strength at the point where the object is

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16
Q

How can the weight of an object be calculated?

A
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17
Q

What are the units for gravitational field strength?

A

Gravitational field strength, g, measured in N/kg

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18
Q

What is an object’s centre of mass?

A

The weight of an object acting at a single point

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19
Q

What does W ∝ m mean?

A

The weight and mass of an object are directly proportional

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20
Q

How is weight measured?

A

A calibrated spring-balance (newton meter)

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21
Q

What is a ‘resultant force’

A

A single force, replacing a number of forces, acting upon an object

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22
Q

What has happened if a resultant force moves an object?

A

Work is done

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23
Q

What is the equation for work done?

A
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24
Q

When a force causes an object to move through a distance what has happened?

A

Work is done on the object so a force does work on an object when the force causes a displacement of the object

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25
Q

What is one joule of work done?

A

When a force of one newton causes a displacement of one metre

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26
Q

What does 1 joule equal?

A

1 newton-metre

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27
Q

What happens to temperature when work done occurs against frictional forces on an object?

A

Temperature increases

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28
Q

How many forces need to change the shape of an object (by bending, stretching or compressing)?

A

More than one

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29
Q

What has happened if an object has been inelastically deformed?

A

It doesn’t return to its original shape and length after a force has been removed

30
Q

What has happened if an object has been elastically deformed?

A

It returns to its original shape and length after a force has been removed

31
Q

What has happened if an object has been elastically deformed?

A

The extension of an elastic object is directly proportional to the force applied

32
Q

What is the equation for force (in relation to elasticity)

A
33
Q

When a spring is compressed what does the ‘e’ in ‘F = k e’ represent?

A

‘e’ would be the compression of the object (the difference between the natural and compressed lengths)

34
Q

Why type of energy is stored when a force does work on a spring?

A

Elastic potential energy

35
Q

What is distance?

A

How far an object moves (a scalar quantity) which does not involve direction

36
Q

What is displacement?

A

Displacement includes both the distance an object moves and the direction (a vector quantity)

37
Q

What does speed not involve?

A

Direction (it is a scalar quantity)

38
Q

What are typical speed values for someone walking, running and cycling (m/s)

A
  • Walking 1.5 m/s
  • Running 3 m/s
  • Cycling 6 m/s
39
Q

Is the speed of sound (and that of the wind) constant?

A

No – the speed of sound (and that of the wind) can vary

40
Q

What is the typical value for the speed of sound (m/s)

A

330 m/s

41
Q

How can distance travelled be calculated?

A
42
Q

What is the velocity of an object?

A

Velocity is speed, in a given direction (a vector quantity)

43
Q

If an object is moving in a straight line how can the distance travelled be represented?

A

Distance-time graph

44
Q

How can the speed of an object be calculated in a distance-time graph?

A

The gradient

45
Q

Annotate the following distance-time graph:

A
46
Q

How can acceleration be calculated?

A
47
Q

What is happening to an object which is slowing down?

A

It is decelerating

48
Q

Draw a velocity-time graph for two vehicles – one with a constant acceleration and one with a constant acceleration, a constant velocity and a constant deceleration

A
49
Q

What is the acceleration of any free-falling object near the Earth’s surface?

A

9.8 m/s2

50
Q

What initially causes an object falling through a fluid to accelerate?

A

The force of gravity

51
Q

Why does an object reach terminal velocity?

A

The resultant force becomes zero

52
Q

What does Newton’s First Law state (for a stationary object)?

A

If the resultant force is zero a stationary object remains stationary

53
Q

What does Newton’s First Law state (for a moving object)?

A

If the resultant force is zero a moving object continues to move at the same velocity

54
Q

How can the forces be described for a vehicle moving at a steady speed?

A

The resistive forces balance the driving force

55
Q

What causes the velocity of an object to change?

A

The resultant force acting on the object must change

56
Q

What is Newton’s Second Law?

A

The acceleration of an object is proportional to the resultant force acting on the object (and inversely proportional to the mass of the object)

57
Q

What is the equation for Newton’s Second Law?

A
58
Q

What are typical everyday speeds for cars, trains and planes?

A
  • Car 25 m/s
  • Train 55 m/s
  • Plane 250 m/s
59
Q

What is Newton’s Third Law?

A

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

60
Q

How can the stopping distance of a vehicle be calculated?

A

The sum of the thinking distance and the braking distance

61
Q

What is thinking distance?

A

The distance covered during the driver’s reaction time

62
Q

What is braking distance?

A

The distance covered during the braking force

63
Q

For a given braking force, what does greater speed cause?

A

A greater stopping distance

64
Q

What are ‘typical’ reaction times?

A

0.2 s to 0.9 s

65
Q

What can affect a driver’s reaction time?

A
  • Tiredness
  • Drugs
  • Alcohol
66
Q

What can affect the braking distance of a vehicle?

A
  • Road conditions
  • Weather conditions (wet / ice)
  • Vehicle conditions (brake / tyre quality etc…)
67
Q

What happens when a force is applied to the brakes of a vehicle (in terms of energy)?

A

Work done by the friction force between the brakes and wheel reduces kinetic energy of the vehicle (and brake temperature increases)

68
Q

How does increases the speed of a vehicle affect the braking force?

A

A greater braking force is needed to stop the vehicle in a given distance

69
Q

What does a greater braking force allow?

A

A greater deceleration

70
Q

What can large decelerations lead to?

A

Brakes overheating / loss of control

71
Q

How is momentum calculated?

A
72
Q

What is the conservation of momentum?

A

In a closed system, the total momentum before an event is equal to the total after an event