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GCSE Physics > Forces and Motion > Flashcards

Forces and Motion Flashcards

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1
Q

What is a distance-time graph?

A

A distance time graph shows how the distance of an object moving in a straight line (from a starting position) varies over time. They also show if the object is moving at a constant speed and how large or small the speed is.

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2
Q

What represents ‘Constant Speed’ on a Distance-Time graph?

A

A straight line (slope).

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3
Q

What can you tell from the slope of a straight line on a distance-time graph?

A

The magnitude of the speed.

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4
Q

What speed is the object moving at if the slope is very steep, shallow, or flat on a Distance-Time graph?

A
  • Large speed
  • Small speed
  • Stationary (not moving)
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5
Q

How is changing speed shown in a Distance-Time graph?

A

a curve - changing slopes.

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6
Q

If a slope on a curve is increasing/decreasing in a Distance-Time graph, what does it show?

A
  • acceleration
  • deceleration
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7
Q

How can the speed of a moving object be calculated in a Distance-Time graph?

A

By the gradient - rise/run.

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8
Q

What is a scalar quantity?

A

A quantity which only contains a magnitude (size) AND NOT direction.

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9
Q

What is a vector quantity?

A

A quantity which contains magnitude (size) AND direction.

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10
Q

What is the equation for calculating speed?

A

Average speed = distance moved/ time taken.

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11
Q

What is acceleration?

A

Acceleration is defined as the rate of change of velocity, it describes how much an object’s velocity changes every second.

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12
Q

What is the equation for acceleration?

A

acceleration = change in velocity/time taken (a = v-u/t

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13
Q

How is change in velocity found?

A

final velocity - initial velocity

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14
Q

What is the motion of an object speeding up/slowing down?

A

Acceleration/deceleration

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15
Q

What does it mean when the acceleration is negative?

A

Decelerating/slowing down.

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16
Q

What is a velocity-time graph?

A

A velocity-time graph shows how the velocity of an object varies with time- if an object is moving with constant acceleration/deceleration AND the magnitude of the acceleration/deceleration.

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17
Q

What does a straight line mean on a velocity-time graph?

A

Constant acceleration.

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18
Q

What does the slope of a line represent in a velocity-time graph? (steep, gentle, flat)

A
  • Large acceleration/deceleration (the object’s speed changes very quickly)
  • Small acceleration/deceleration (the object’s speed changes very gradually)
  • Zero acceleration (the object is moving with a constant velocity)
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19
Q

How can the acceleration of an object be calculated from a velocity-time graph?

A

Through the gradient (rise/run).

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20
Q

What is displacement?

A

The distance and direction travelled by an object.

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21
Q

How can you find the displacement in a velocity-time graph?

A

From the area under a velocity-time graph.

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22
Q

What are the effects of forces?

A
  • Changes in speed: forces can cause bodies to speed up or slow down
  • Changes in direction: forces can can cause bodies to change their direction of travel
  • Changes in shape: forces can cause bodies to stretch, compress, or deform.
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23
Q

What is an applied force?

A

Push/pull

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24
Q

What is a frictional force?

A

friction always acts in the opposite direction to motion and emerges when two or more surfaces rub against each other. This happens because of the way imperfections (not perfectly smooth) on the two surfaces at the molecular level push against each other

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25
Q

What is a gravitational force?

A

the gravitational force we feel is called our weight- all masses attract other masses.

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26
Q

What is normal reaction force?

A

when an object rests on a solid, it feels a reaction force at 90 degrees to the surface.

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27
Q

What is air resistance (drag)?

A

Drag occurs when an object moves through fluid(air resistance in air). Drag is affected by the object’s shape, the fluid it travels in and its speed.

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28
Q

What is thrust?

A

Thrust is a reaction force, it occurs when mass is pushed out the back of something, causing the object to move forwards, e.g. rockets, letting go of a balloon and jet engines.

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29
Q

What is tension?

A

Tension acts in strings, chains and cables when they are stretched- the force always acts parallel to the string. The opposite of tension is compression.

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30
Q

What is up-thrust?

A

Upthrust can only occur in fluids and is the reason things float. It is not the same as normal reaction force. Only when the object is in a fluid.

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31
Q

What is lift?

A

Lift is the force produced due to the flow of a fluid over an aerodynamic surface. In an aircraft it acts against the gravitational pull.

32
Q

What is spring force?

A

A force required to stretch or compress a spring. The stretching force is directly proportional to the extension.

33
Q

What is electric force?

A

The attraction between oppositely charged objects/ the repulsion between similarly charged objects.

34
Q

What is Magnetic force?

A

Magnetic attraction(2 opposite poles)/ magnetic repulsion (two similar poles).

35
Q

Is distance a scalar or vector?

A

Scalar

36
Q

Is displacement a scalar or vector?

A

Vector

37
Q

Is force a vector or a scalar?

A

Vector

38
Q

What is resultant force?

A

A resultant force is a single force that describes all of the forces operating on a body.

39
Q

What does a resultant force define?

A

The direction and the magnitude.

40
Q

How can resultant forces be calculated?

A

By adding or subtracting all of the forces acting on the object. Forces working in opposite directions are subtracted from each other and forces working in the same direction will be added together.

41
Q

What does it mean if the forces acting in opposite directions are equal in size?

A

There will be no resultant force- the forces are said to be balanced.

42
Q

What is friction?

A

The force which opposes the motion of an object.

43
Q

What are balanced forces?

A

Balanced forces mean that the forces have combined in such a way that they cancel each other out and no resultant force acts on the body.

44
Q

What is an example of a balanced force?

A

A book resting on a table.

45
Q

What are unbalanced forces?

A

Unbalanced forces mean that the forces have combined in such a way that they do not cancel out completely and THERE is a resultant force on the object.

46
Q

What is an example of an unbalanced force?

A

A tug-of-war.

47
Q

What is the equation to find out force?

A

force (resultant) = mass * acceleration

48
Q

What is force measured in?

A

Newtons (N).

49
Q

What is mass measured in?

A

kilograms (kg)

50
Q

What is acceleration measured in?

A

m/s^2

51
Q

What is weight?

A

The force acting on an object due to gravitational attraction.

52
Q

What is the equation for weight?

A

W = mg

53
Q

What is weight measured in?

A

Newtons.

54
Q

What is gravitational field strength measured in?

A

m/s^2 OR N/kg

55
Q

What is stopping distance?

A

The total distance travelled during the time it takes for a car to stop in response to some emergency.

56
Q

What is the equation for stopping distance?

A

Stopping distance = Thinking distance + Braking distance

57
Q

What is the thinking distance?

A

the distance travelled in the time it takes the driver to react (reaction time) in metres (m)

58
Q

What is the braking distance?

A

the distance travelled under the braking force in metres (m)

59
Q

The greater the speed of the vehicle….

A

the greater the stopping distance.

60
Q

What are factors affecting stopping distance?

A

Vehicle speed, vehicle mass, road conditions, driver reaction time

61
Q

How does vehicle speed affect stopping distance?

A

the greater the speed, the greater the vehicle’s braking distance will be (because the brakes will need to do more work to bring the vehicle to a stop).

62
Q

How does the vehicle mass affect stopping distance?

A

a heavy vehicle, such as a lorry, takes longer to stop.

63
Q

How does road conditions affect stopping distance?

A

wet or icy roads make it harder to decelerate.

64
Q

How does driver reaction time affect stopping distance?

A

a driver’s thinking distance depends on their reaction time. Being tired, or intoxicated(i.e. alcohol, or drugs) can increase reaction time.

65
Q

Which two forces do falling objects experience?

A
  • weight (due to gravity)
  • air resistance (due to friction)
66
Q

What increases with speed?

A

the force of air resistance.

67
Q

What happens to Debbie when she leaves the aircraft to skydive?

A

She initially accelerates downwards due to her weight. The upwards air resistance increases as she falls until it eventually grows big enough to balance the weight force.

68
Q

Describe Debbie’s motion as she parachutes downwards. (STAGE 1)

A

Just after jumping, there is little air resistance acting on her, so she accelerates. However, her weight acts downwards which is why there is a large resultant force downwards, which is why the sky diver accelerates.

69
Q

Describe Debbie’s motion as she parachutes downwards. (STAGE 2)

A

She is still accelerating, but not as much as before. She is now moving downwards, so she experiences an air resistance force upwards. Her weight is the same as ever. Her resultant force is downwards, but it is not as large as before.

70
Q

Describe Debbie’s motion as she parachutes downwards. (STAGE 3)

A

She is moving at constant velocity(speed and direction). As her speed increases, the air resistance increases until it was equal in size to her weight. At this point, there was no longer any resultant force. With no resultant force, her velocity (speed and direction) stays the same (until she either hits the ground or opens the parachute).

71
Q

Describe Debbie’s motion as she parachutes downwards. (STAGE 4)

A

She is decelerating. When she opens the parachute, her air resistance increases dramatically (because of the parachute’s larger area). It now exceeds her weight, and so there is a resultant force upwards. This does not make her move upwards; it eats away at her downward speed.

72
Q

Describe Debbie’s motion as she parachutes downwards. (STAGE 5)

A

She is decelerating but at a lower rate. She has slowed down, so her air resistance has decreased. The resultant upwards force is therefore less than before.

73
Q

Describe Debbie’s motion as she parachutes downwards. (STAGE 6)

A

Her velocity is constant (until it hits the ground). This new terminal velocity is lower than the previous terminal velocity when she was in free fall. As her speed decreased, the air resistance decreased until it was equal in size to her weight, again. At this point, there was no more resultant force and her velocity no longer changed.

74
Q

How to set up an investigation to find the motion of an object?

A

a buggy moving down a slope. The buggy will have different weights on it- 10N, 20N and so forth, the weights pulling the buggy will also vary. This will be measured through light gates- giving the acceleration. f= m * a

75
Q

How can you tell acceleration and deceleration through ticatape?

A

Ticker timers and tape create representations of motion in a straight line. A strip of tape is attached to a moving object, such as your hand, and passed through the timer. The timer marks the tape with a dot at regular time intervals. Different speeds result in different distances between the dots. Far apart = accelerating
close together = decelerating
same distance apart = constant speed

GCSE Physics (5 decks)

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