Forces and Motion Flashcards

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1
Q

Can forces be seen?

A

No, but the effect of forces can be seen.

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2
Q

How many objects are required for a force to be applied?

A

Two

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3
Q

What are 3 effects can a force have on an object?

A

It can change the shape of an object or it can change the object’s motion (speed and/or direction).

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4
Q

What does the word ‘Motion’ refer to in physics?

A

The speed and/or direction of an object.

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5
Q

In what 3 ways can a force deform (change the shape) of an object?

A

Compress (squash)

Extend (stretch)

Bend / twist

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6
Q

In what 4 ways can a force change the motion of an object?

A

Increase speed (accelerate)

Decrease speed (decelerate)

Maintain constant speed

Change direction

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7
Q

All forces come in pairs. What can be said about the two forces in a force pair?

A

They are the same type of force.

They are the same size.

They act in opposite directions.

They act on different objects

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8
Q

Complete the following statement about two forces in a force pair:
A pencil pushes down on a piece of paper, the paper pushes…

A

A pencil pushes down on a piece of paper.
The paper pushes up on the pencil.

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9
Q

Complete the following statement about two forces in a force pair:
A jet pushes exhaust gases backwards…

A

A jet pushes exhaust gases backwards.
The exhaust gases push the jet forwards.

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10
Q

Complete the following statement about two forces in a force pair:
The Earth pulls down on the Moon due to gravity…

A

The Earth pulls down on the Moon due to gravity.
The Moon pulls up on Earth due to gravity.

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11
Q

What do we call forces that can be applied at a distance, even when objects are not touching?

A

Non-contact forces

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12
Q

What do we call forces that require objects to be touching to be applied?

A

Contact force

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13
Q

Name the three non-contact forces.

A

Magnetic

Electrostatic

Gravitational (Weight)

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14
Q

Describe: Applied force

A

A person pushing or pulling an object.

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15
Q

Describe: Tension

A

A force in a rope or cable being pulled.

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16
Q

Describe: Reaction force

A

Force from a surface that opposes an action upon it.

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17
Q

Describe: Friction

A

A force between two surfaces that opposes motion.

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18
Q

Describe: Drag

A

A force that opposes motion in fluids (liquids and gases).

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19
Q

Describe: Air resistance

A

A force that opposes motion in air.

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20
Q

Describe: Water resistance

A

A force that opposes motion in water.

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21
Q

Describe: Weight

A

Downwards force due to gravity

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22
Q

Describe: Upthrust

A

The upwards force of water on a (floating) object.

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23
Q

Describe: Lift

A

The upwards force that stops aeroplanes falling to Earth.

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24
Q

Describe: Normal contact force

A

The name of the force that stops objects falling through solid objects.

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25
Q

Describe: Spring force

A

Force a deformed object exerts against the object that changes its shape.

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26
Q

Is air resistance a contact or non-contact force?

A

Contact force - air particles must touch an object to exert the force.

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27
Q

What units are forces measured in?

A

Newtons (N)

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28
Q

What do we draw to show the forces acting on an object?

A

A force diagram

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29
Q

On a force diagram, what shape is used to represent a force.

A

An arrow.

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30
Q

What does the length of an arrow on a force diagram represent?

A

The size of the force.

31
Q

What does the direction of an arrow on a force diagram represent?

A

The direction of the force.

32
Q

What do we call it when two forces are acting on one object and are equal in size but act in opposite directions?

A

Balanced forces

33
Q

What do we call it when two forces are acting on one object and are not equal in size but act in opposite directions?

A

Unbalanced forces

34
Q

What one word could be used to describe the two forces acting on the rope here?

A

Balanced

35
Q

What one word could be used to describe the two forces acting on the rope here?

A

Unbalanced

36
Q

What happens to an object when the forces acting on it are balanced?

A

There is no change in the object’s motion (speed or direction)

37
Q

What is the name for the overall force when you add (or subtract) all the forces acting on an object?

A

The resultant force

38
Q

What is the resultant force when forces on an object are balanced?

A

Zero

39
Q

What three things can happen when the resultant force on an object is not zero?

A

It speeds up (accelerates)

It slows down (decelerates)

It changes direction

40
Q

Name the piece of equipment used to measure forces in the classroom.

A

Newtonmeter

41
Q

What unit do we use to measure distance?

A

Metres (m)

42
Q

What unit do we use to measure time?

A

Seconds (s)

43
Q

What unit do we use to measure speed?

A

Metres per second (m/s)

44
Q

What does 1m/s mean?

A

One metre is travelled every second.

45
Q

In words, what equation links speed, distance and time?

A

speed = distance ÷ time

46
Q

In symbols, what equation links speed, distance and time?

A

s = d ÷ t

47
Q

What is a distance-time graph?

A

A graph showing how an object’s speed changes over time.

48
Q

What does a horizontal line on a distance-time graph mean?

A

The speed is zero (the object is stationary)

49
Q

What does a slope on a distance-time graph mean?

A

The object is moving

50
Q

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

A

Speed is constant.

51
Q

Sketch a distance-time graph of an object that moves away from its starting point at constant speed

A
52
Q

Sketch a distance-time graph of an object that moves away from its starting point at a high constant speed, stops for a period, then returns to the starting point at low constant speed.

A
53
Q

How can speed be calculated from a distance-time graph?

A

The gradient

54
Q

What does relative motion mean?

A

The speed of a moving object from the viewpoint of another moving object

55
Q

If two objects move in the same direction, how can you calculate their relative speed?

A

Subtract their individual speeds from one another.

56
Q

If two objects move in opposite directions, how can you calculate their relative speeds?

A

Add their individual speeds to one another.

57
Q

What is the difference between mass and weight?

A

Mass is a measure of how much matter is in an object in kg.
Weight is a measure of the downwards force on a mass due to gravity in N.

58
Q

If an object moves from one planet to another, does its mass change?

A

No

59
Q

If an object moves from one planet to another, does its weight change?

A

Yes

60
Q

In words, what equation links weight, mass and gravitational field strength?

A

Weight = mass x gravitational field strength

61
Q

In symbols, what equation links weight, mass and gravitational field strength?

A

W = m x g

62
Q

What unit do we use to measure mass?

A

Kilogram (kg)

63
Q

What unit do we use to measure weight?

A

Newtons (N)

64
Q

What unit do we use to measure gravitational field strength?

A

Newtons per kilogram (N/kg)

65
Q

What is gravitational field strength on Earth (approximately)?

A

10 N/kg

66
Q

How can we squash an object?

A

Push on opposite sides of the object

67
Q

How can we stretch an object?

A

Pull on opposite sides of the object

68
Q

What do we call the change in size when an object is squashed?

A

Compression

69
Q

What do we call the change in size when an object is stretched?

A

Extension

70
Q

How can we calculate extension?

A

Extension = stretched length - original length

71
Q

What units do we use to measure extension?

A

Metres (m)

72
Q

What do we call a material that returns to its original size after the forces changing its shape are removed?

A

Elastic material

73
Q

What is the relationship between force and extension for an elastic material?

A

As force doubles, extension doubles (Directly proportional)

74
Q

What do we call the point after which a material will not return to its original shape (permanently deformed)?

A

Elastic limit