P4 Flashcards

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1
Q

What is the formula for speed?

A

Distance traveled (m) / time taken (s)

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2
Q

What is speed measured in?

A

m/s

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3
Q

What is it called if you measure average speed over a very short time period?

A

Instantaneous speed.

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4
Q

What is the displacement of an object?

A

The distance from its start point to the straight line?

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5
Q

How is displacement expressed?

A

As a distance with a direction.

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6
Q

Are displacement and velocity scalar or vector quantities?

A

Both vector.

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7
Q

What is the velocity of an object?

A

It’s speed in a certain direction.

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8
Q

What is the formula for average velocity?

A

displacement/time taken.

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9
Q

What is a distance-time graph used for?

A

To visualize a journey.

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10
Q

In a distance-time graph, what is plotted against the y-axis and what is plotted against the x-axis?

A

Y-axis : the time

X -axis: the distance travelled

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11
Q

In a distance-time graph, what does a horizontal line mean?

A

The vehicle is stationary.

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12
Q

In a distant-time graph, what is the gradient of the line equal to?

A

The speed.

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13
Q

In a distant-time graph, the steeper the gradient…

A

the faster the speed.

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14
Q

In a distant-time graph, what does a curved line mean?

A

The speed is changing.

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15
Q

In a distant-time graph, what does it mean if a curve is getting steeper?

A

the vehicles speed is increasing.

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16
Q

What is a displacement time-graph used for?

A

To visualize return journeys.

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17
Q

What is acceleration?

A

The rate at which the speed of an object increases.

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18
Q

What is acceleration measured in?

A

m/s^2

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19
Q

Acceleration=

A

change in speed (m/s) / time taken (s)

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20
Q

What is deceleration?

A

When an object slows down.

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21
Q

What has to be acting on an object to cause acceleration (or deceleration)?

A

A force.

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22
Q

When the net or overall force is zero, the acceleration is…

A

zero.

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23
Q

What is a speed-time graph used for?

A

to show the changes in speed during a journey.

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24
Q

In a speed-time graph, what is plotted on the x-axis and what is plotted on the y-axis?

A

Y axis: speed

X axis: time

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25
Q

In a speed-time graph, what does a horizontal line mean?

A

constant speed.

26
Q

What does a velocity-time graph show?

A

the direction in which an object is travelling?

27
Q

What does a positive and negative velocity mean?

A

Negative velocity: the object is travelling in a negative direction.
Positive velocity: the object is travelling in a certain direction

28
Q

What is a force?

A

A push or pull which acts between two objects.

29
Q

Forces always act in…

A

pairs.

30
Q

What does a repulsive force do?

A

Pushes objects apart.

31
Q

What does an attractive force do?

A

Pulls objects towards each-other.

32
Q

Are forces vector or scalar quantities?

A

Vector.

33
Q

How is force represented on a diagram?

A

With an arrow.

34
Q

What is friction?

A

A force that acts between two surfaces.

35
Q

What does the side of the friction force depend on?

A
  • the roughness of the surfaces (rougher surfaces give more friction).
  • how hard the surfaces are pushed together (the heavier the object the more friction).
36
Q

What is limiting friction?

A

When the friction reaches a maximum value.

37
Q

Why do you need friction to walk?

A

When you walk your feet push against the friction, pushing your foot forwards.

38
Q

What is resultant force?

A

The total or overall force acting on an object.

39
Q

What happens when the resultant force is equal to 0?

A

the forces are balanced.

40
Q

What speed do objects accelerate to the ground at as a result of gravity?

A

9.8 m/s^2.

41
Q

What is the upwards force that slows down falling objects?

A

Air resistance or drag?

42
Q

What is drag?

A

The force that acts in the opposite direction to the speed.

43
Q

Drag force increases as…

A

the speed of the object increases.

44
Q

The larger the surface area of the object…

A

the larger the drag force.

45
Q

What is terminal velocity?

A

When the constant maximum speed is reached by a falling object.

46
Q

What does the size of the force depend on?

A
  • the mass of the object.
  • the speed of the object.
  • the duration of the impact.
47
Q

What are car safety devices, e.g. air bags, crumple zones and seat belts, designed for?

A

to reduce the impact time, thus reducing the force in a collision.

48
Q

What is the momentum formula?

A

Mass x velocity

49
Q

What is the formula for change in momentum?

A

resultant force x time for which it acts.

50
Q

What is the formula for force?

A

Change in momentum / time taken.

51
Q

What is work(done)?

A

The energy used by the movement of a force?

52
Q

What is energy and work measured in?

A

Joules (J).

53
Q

What is the formula for work done?

A

Force x Distance moved in the direction of the force

54
Q

What is the same as work done?

A

Amount of energy transferred.

55
Q

When you lift an object…

A

you do work against gravity.

56
Q

When you life an object, the work done is transferred to…

A

GPE.

57
Q

What is the formula for Kinetic energy?

A

1/2 x mass x velocity^2.

58
Q

What is the formula for Work done?

A

force x distance moved.

59
Q

What is the principle of the conservation of energy?

A

When there are no resistive forces the total energy remains constant.

60
Q

Energy cant be either created or destroyed…

A

it can only be transferred/(change form).