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Flashcards in Forces Deck (112):
1

What is a vector?

A quantity that has a magnitude and direction

2

What is a scalar?

A quantity that only has a magnitude but not a direction

3

Give some examples of vector quantities.

Force
Velocity
Displacement
Acceleration
Momentum

4

Give some examples of scalar quantities.

Speed
Distance
Mass
Temperature
Time

5

Define the term force.

A push or a pull on an object that is caused by it interacting with something

6

What is a contact force?

When two objects have to be touching for a force to act

7

What is a non-contact force?

When two objects do not need to be touching for a force to act

8

What is an interaction pair?

A pair of forces, acting on two interacting objects, that are equal and opposite

9

What is gravitational force?

The force of attraction between masses

10

True or false?

Gravity attracts all masses but you only notice it when the mass is really big.

True

11

Give 2 important effects of gravity.

On the surface of a planet, it makes all things fall to the ground
It gives everything a weight

12

How are mass and weight different?

Mass is the amount of 'stuff' in an object
Weight is the force acting on an object due to gravity

13

What is the gravitational field strength on Earth?

9.8N/kg

14

What is the gravitational field strength on moon?

1.6N/kg

15

What is an object's centre of mass?

The single point on an object where you can think of weight acting from

16

True or false?

Mass and weight are inversely proportional.

False
They're directly proportional

17

Give the equation that links mass and weight.

Weight = Mass x Gravitational Field Strength

18

What is resultant force?

The equivalent of just one force acting in a single direction when forces add or subtract their quantities because there are multiple forces acting on an object

19

What is a free body diagram?

A diagram that shows all the forces acting on an object but none of the forces that the object exerts on the rest of the world

20

True or false?

When a force moves an object through a distance, energy is transferred and work is done on the object.

True

21

Give the equation linking work done and force.

Work done = Force x Distance

22

Convert 1 joule into newton metres.

1Nm

23

How would you use a scale drawing to find resultant force?

1) Draw all of the forces acting on an object to scale, using arrows
2) Draw the resultant force with a line starting at the tail of the first arrow and finishing at the tip of the second arrow
3) Measure the length of the resultant force arrow with a ruler
4) Find the bearing that the force is acting at using a protractor

24

What is meant by resolve a force?

Split it into horizontal and vertical components

25

Apart from moving, what can applying a force to an object make it do?

Stretch
Compress
Bend

26

Define the term elastic deformation.

An object can return to its original shape and length after the force has been removed

27

Give an example of an object that can be elastically deformed.

A spring

28

Define the term inelastic deformation.

An object cannot return to its original shape and length after the force has been removed

29

Give the equation linking force and extension.

Force = Spring constant x Extension

30

True or false?

Extension is directly proportional to force.

True
But there is a limit of proportionality - it stops being proportional after a certain point

31

Describe the steps for the investigation of the link between force and extension

- Measure the natural length of the spring (without masses) with a millimetre ruler clamped to a stand
- Add a mass to the spring and allow it to come to rest
- Record the mass and measure the new length of the spring
- Repeat the process until you have enough measurements (no less than 6)

32

In the practical investigating the link between force and extension, how can you make sure you won't pass the spring's limit of proportionality?

Using an identical spring, load it with masses one at a time up to a total of five and record the increase in extension each time - if the extension increase is bigger than the last then you've past the limit

33

What would you do if the masses in the force-extension investigation past the limit of proportionality?

Use smaller masses

34

How can you ensure accuracy in the force-extension investigation?

Take the readings at eye level
Use a marker (e.g. a bit of tape) at the bottom of the spring

35

What do you do with the results from the force-extension practical?

Plot them on a force-extension graph: if the relationship is linear, the gradient is equal to spring constant and the area under the graph is equal to how much energy is in the elastic potential store

36

Give the equation to calculate elastic potential energy.

Elastic potential energy = 0.5 x Spring constant x (Extension)^2

37

What is a moment?

The turning effect of a force

38

Give the equation to calculate the size of a moment.

Moment = Force x Distance

39

What is a lever?

Something that increases the distance from the pivot at which force is appled

40

Give two examples of simple levers.

Long sticks or bars
Wheelbarrows

41

What are gears?

Circular discs with 'teeth' around their edges

42

What are gears used for?

To transmit the rotational effect of a force from one place to another by interlocking their 'teeth' and causing the next gear to turn in the opposite direction

43

True or false?

A larger gear will move quicker than a smaller gear.

False
It will move slower

44

Give the equation for pressure.

Pressure = Force ÷ Area

45

Define the term fluid.

A substance that can 'flow' because their particles are able to move around
A liquid or a gas

46

True or false?

Particles exert a force on containers.

True

47

What is density a measure of?

The 'compactness' of a substance
How close together the particles in a substance are

48

True or false?

Density does not vary through a given liquid but the density of a gas can vary.

True

49

Why does pressure of a liquid depend on depth?

Because as the depth increases, the number of particles above that point increases so the weight of those particles adds to the pressure

50

What is upthrust?

A force that determines whether an object will float or sink when in fluid

51

Why do objects experience upthrust in fluids?

Because the fluid exerts a force on it from all directions, but more on the bottom because the pressure is higher with depth, which causes an upwards resultant force

52

True or false?

An object sinks if its weight is equal to upthrust.

False
It floats - an object sinks if its weight is more than upthrust

53

Link density to sinking or floating.

If an object is more dense than the fluid it's placed in, it will sink
If an object is less dense than the fluid it's placed in, it will float

54

Explain how submarines make use of upthrust.

To sink, large tanks are filled with water to increase the weight
To float, large tanks are filled with compressed air to decrease the weight

55

What is the atmosphere?

A layer of air that surrounds the Earth

56

How is atmospheric pressure created?

The air molecules of the atmosphere collide with a surface to exert pressure on it

57

True or false?

As altitude increases, atmospheric pressure decreases.

True

58

Explain why atmospheric pressure decreases with increasing altitude.

The atmosphere gets less dense so there are fewer air molecules to collide and so exert pressure
There are fewer air particles above a surface with increasing height meaning the weight of air above it is less and so the force it exerts is smaller, causing pressure to be smaller too

59

Give the formula for speed.

Speed = Distance ÷ Time

60

What is the typical speed of walking?

1.5m/s

61

What is the typical speed of running?

3m/s

62

What is the typical speed of cycling?

6m/s

63

What is the typical speed of a car?

25m/s

64

What is the typical speed of a train?

55m/s

65

What is the typical speed of a plane?

250m/s

66

What is the speed of sound?

330m/s in air

67

List four factors that can affect how fast an individual moves.

Age
Fitness
Distance travelled
Type of terrain

68

List two factors that can affect how fast sound travels.

What the sound waves are travelling through
Speed of wind

69

List three factors that can affect how fast wind travels.

Temperature
Atmospheric pressure
Proximity to large buildings or structures

70

Define the term acceleration.

The rate of change of velocity

71

Give the equation for acceleration.

Acceleration = Change in velocity ÷ Time

72

What, roughly, is the acceleration of objects in freefall?

9.8m/s^2

73

True or false?

Acceleration due to gravity is uniform in free fall.

True

74

What does the gradient of a distance-time graph show?

The speed

75

What does the gradient of a velocity-time graph show?

The acceleration

76

What does the area under a velocity-time graph show?

The distance travelled

77

What is drag?

Frictional forces within a fluid

78

Give an example of drag.

Air resistance

79

How do you reduce drag?

Make an object streamlined

80

Give an example of an object that wants to maximise drag.

Parachutes

81

True or false?

Friction increases with speed.

True

82

What is terminal velocity?

Maximum speed
The point in which the resultant force between friction and the accelerating force is zero

83

True or false?

Terminal velocity doesn't depend on shape and area.

False
It does depend on it

84

Give the equation for weight.

Weight = Mass x Gravitational field strength

85

What does Newton's First Law state?

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'll just carry on moving at the same velocity

86

What does Newton's Second Law state?

Resultant force and acceleration are directly proportional
Acceleration and mass are inversely proportional

87

Give the equation linking force and acceleration.

Force = Mass x Acceleration

88

Define the term inertia.

The tendency for motion to remain unchanged
The ratio of force over acceleration

89

What does Newton's Third Law state?

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

90

Describe how to set up the apparatus for the investigation for motion.

- Set up a trolley of known mass to hold a bit of card with a gap in the middle
- Along the table set up a light gate connected to a data logger or a computer
- Connect the trolley to a bit of string that goes over a pulley and is connected on the other side to a hook (of known mass) which can have more masses added to it
- Mark a starting line on the table

91

Describe how you would carry out the investigation for motion.

- Place the trolley on the starting line and hold it in place, allowing the hook and any extra masses to hang
- Release the trolley
- Record the acceleration measured by the light gate, which is the acceleration of the whole system
- Repeat the experiment twice more to get an average acceleration

92

What would you do to investigate how mass affects motion in the required practical?

Add masses to the trolley, one at a time, and record the average acceleration for each mass

93

What would you do to investigate how force affects motion in the required practical?

Start with all the masses on the trolley, as the total mass of the system cannot change, and transfer the masses onto the hook one at a time, recording the average acceleration for each force

94

What is stopping distance a measure of?

How far a car travels during an emergency stop

95

Give the equation for stopping distance.

Thinking distance + Stopping distance

96

List two factors that affect thinking distance.

Speed
Reaction time

97

Give four things that can affect reaction time.

Tiredness
Alcohol
Drugs
Distractions

98

List four factors that affect braking distance.

Speed
Weather or road surface
Condition of tyres
Quality of brakes

99

How long is a typical reaction time?

Between 0.2 and 0.9 seconds

100

Describe how to carry out the ruler drop test.

- Sit with your arm resting on a table
- Get someone to hold a ruler so it hangs between your thumb and forefinger, lined up with zero
- The person holding the ruler should drop it without any warning
- The person catching should close their thumb and forefinger as quickly as possible
- Record the measurement on the ruler that you caught it at
- Repeat as many times as possible

101

What are control variables in the ruler drop test?

Use the same ruler
Have the same person dropping it

102

What could you change about the ruler drop test?

Whether there are distractions or not

103

How does braking work?

Brake pads are pressed onto wheels which causes friction between the movement of the wheel and the surface of the brake pad

104

Large braking forces mean large decelerations. Why are large decelerations dangerous?

They may cause brakes to overheat
They may cause the vehicle to skid

105

What is the typical stopping distance for a car travelling at 30mph?

23m
6 car lengths

106

What is the typical stopping distance for a car travelling at 50mph?

53m
13 car lengths

107

What is the typical stopping distance for a car travelling at 70mph?

96m
24 car lengths

108

True or false?

Speed affects thinking distance more than braking distance.

False
It affects braking distance more than thinking distance

109

Give the equation to calculate momentum.

Momentum = Mass x Velocity

110

What does the conservation of momentum law state?

In a closed system, the total momentum before an event is the same as after the event

111

Cars have safety features to reduce the chance of injury during a crash. Give three examples of them.

Crumple zones
Seatbelts
Air bags

112

What do helmets have as a safety feature?

A crushable layer of foam