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