Flashcards in 5. Forces Deck (121):

1

## What is a scalar?

### Quantities that are fully described by magnitude or size

2

## What are vectors?

### Quantities that are fully described by both a magnitude and direction

3

## What is distance?

### A scalar quantity that refers to 'how much ground an object has covered'

4

## What is displacement?

### A vector quantity that refers to 'how far out of place an object is'

5

## What is magnitude?

### Size

6

## How can vectors be drawn?

### Using arrows

7

## Is time a vector or scalar quantity?

### scalar

8

## Is force a vector or scalar quantity?

### Vector

9

## Is friction a vector or scalar quantity?

### Vector

10

## Is weight a vector or scalar quantity?

### Vector

11

## Is displacement a vector or scalar quantity?

### Vector

12

## Is distance a vector or scalar quantity?

### Scalar

13

## Is density a vector or scalar quantity?

### Scalar

14

## Is energy a vector or scalar quantity?

### Scalar

15

## Is frequency a vector or scalar quantity?

### Scalar

16

## Is mass a vector or scalar quantity?

### Scalar

17

## Is power a vector or scalar quantity?

### Scalar

18

## Is voltage a vector or scalar quantity?

### Scalar

19

## Is volume a vector or scalar quantity?

### Scalar

20

## What is the gradient on a distance-time graph?

### Velocity

21

## What is the gradient on a velocity-time graph?

### Acceleration

22

## What is the area under a velocity-time graph?

### The distance

23

## What is acceleration?

### When an object speeds up or changes direction

24

## What is the total area underneath a velocity-time graph?

### The total distance travelled

25

## What is the unit of force?

### Newtons, N

26

## Examples of contact forces?

###
• Friction

• Air / Water resistance (drag)

• Normal contact (reaction)

• Tension

• Upthrust

27

## Examples of non-contact forces?

###
• Gravity

• Magnetic

• Electrostatic

28

## What happens when the resultant force on an object is zero?

### The object remains stationary or continues to move at a constant speed and in the same direction.

29

## What is enersher?

### The idea that without an unbalanced force, nothing will change in terms of speed, direction etc.

30

## What is Newton's 1st law of motion?

### An object will remain at rest or at a constant velocity unless there is a resultant force acting on it.

31

## What is Newton's 2nd law of motion?

### The acceleration of an object is directly proportional to the resultant force and inversely proportional to the objects mass.

32

## What equation shows Newtons 2nd law of motion?

### F = m a

33

## What is Newton's 3rd law of motion?

### If object A exerts a force on object B, then object B exerts a force on object A which is equal and opposite.

34

## How is inertial mass defined?

###
By the ratio of force over acceleration

(if an object is more inert then it's harder to move)

35

## What is thinking distance proportional to?

### Speed

36

## What is braking distance proportional to?

### Speed2

37

## What is thinking distance?

### The distance travelled during reaction time.

38

## What is braking distance?

### The distance travelled while the brakes are applied.

39

## Why does thinking distance increase?

###
• the speed increases

• the reaction time increases eg. tiredness, distraction, taken drugs / alcohol

40

## When does braking distance increase?

### If the initial speed increases or if the size of deceleration is less.

41

## How is thinking distance decreased?

### Friction reduced - wet roads, worn tyres or brakes

42

## How is braking distance decreased?

### Larger mass of car (more inertia means its harder to stop)

43

## How is thinking distance shown on a graph?

### Area of the rectangle underneath the graph

44

## How is braking distance shown on a graph?

### Area of the triangle underneath the graph

45

## Typical speed of walking?

### 1.5 m/s

46

## Typical speed of running?

### 12 m/s

47

## Typical speed of driving?

### 20 m/s

48

## Typical speed of flying?

### 200 m/s

49

## Speed of sound in air?

### 3x10 squared

50

## Speed of light?

### 3x10 to the 8

51

## What is the weight of an object?

### The force of gravity on it

52

## How to convert from Kg to N?

### x10

53

## When does an object reach constant velocity?

### When the drag force is equal and opposite to its weight

54

## What is terminal velocity?

### When an object reaches a constant velocity because the drag force is equal and opposite to its weight

55

## What happens to the drag force when an object is released in a fluid before its terminal velocity?

### The drag force is less than its weight before it reachers terminal velocity

56

## What happens to acceleration when an object is released in a fluid after its terminal velocity?

### It is equal to zero

57

## What happens to the resultant force on an object released in a fluid initially?

### The resultant force is equal to its weight, initally

58

## When an object is falling, what does it initially accelerate at?

### 10 m/s2

59

## What are plastic objects?

### Objects that do not regain their original shape when the forces deforming it are removed

60

## What are elastic objects?

###
An object that regains its original shape when the forces deforming it are removed

It stores elastic potential energy when work is done on the object

61

## Does an elastic collision lose kinetic energy?

### No

62

## What does Hooke's law state?

### That the extension of a spring is in direct proportion with the force applied to it

63

## What is the spring extension?

### New length - original length

64

## What does hooke's law only apply to?

### Elastic materials

65

## What happens to a spring if the force added on the spring is larger?

### It not longer obeys hooke's law and does not return to its original length

66

## What is elastic limit?

### The limit of proportionality (when hooke's law no longer applies)

67

## What is stopping distance?

### Thinking distance + braking distance

68

## What are the two SUVAT equations?

###
v = u + at

v2 = u2 - 2as

69

## What are the two ways of increasing the turning effect of a force?

###
• increase the size of the force

• increase the distance from the pivot

70

## What is the turning effect of a force called?

### A moment

71

## What is the equation to calculate the size of a moment?

### M=Fd

72

## What are moments measured in?

### Nm

73

## When will a seesaw balance in terms of moments?

### When the anticlockwise moment is equal to the clockwise one

74

## What does the principle of moments state?

### For a balanced object, clockwise moments = anticlockwise moments

75

## What is the centre of mass of an object?

### The point at which the mass may be thought to be concentrated

76

## Where does the centre of mass lie in symmetrical objects?

### Along the line of symmetry

77

## Where will the COM be when an object has more than one line of symmetry?

### Where the lines of symmetry intersect

78

## Where will the centre of mass be of a suspended object?

### The centre of mass will be directly below the point of suspension

79

## How can the COM of an irregular shape be found?

###
• by hanging the shape from a point and a plumb line is used to draw a vertical line downwards from the pivot

• this is repeated from different points

80

## What is the stability of an object affected by?

###
• the width of the base of the object

• the height of it's centre of mass

81

## When will an object not topple over?

### When the line of action is within the base

82

## What are the three types of equilibrium when a force is applied to objects?

###
• stable equilibrium - tilts and falls back to original position

• unstable equilibrium - tilts and falls

• neutral equilibrium - rolls

83

## What happens to the centre of mass when a stable object is tilted?

### It is raised

84

## What happens to the centre of mass when an unstable object is tilted?

### It is lowered

85

## What happens to the centre of mass when a neutral object is tilted?

### It stays at the same level if pushed

86

## What does the pressure of a liquid depend on?

### The depth and the density

87

## What is the equation for the pressure at a certain depth due to the column of liquid?

### pressure = depth x field strength x density

88

## What is the nature of liquid pressures at different places, but at the same depth?

### The pressure acts in all directions and is the same depth

89

## What is the nature of liquid pressures at different depths?

### The greater depth, the higher the pressure so the water is pushed down with a greater force and has a bigger horizontal range

90

## What is a gear?

### A rotating machine with cogs that mesh with another toothed part to transmit a moment

91

## What do gears act as?

### A force multiplier

92

## What is a force multiplier?

### Machines designed to increase the size of the force

93

## What is a distance multiplier?

### Machines designed to increase the distance or speed with which something moves

94

## What effort and load do force multipliers involve?

###
• small effort (input force)

• larger load (output force)

95

## Equation for mechanical advantage?

### load / effort

96

## Example of a force multiplier?

### Lever with a distance from pivot to effort 3 times greater than distance from pivot to load - mechanical advantage is 3

97

## How is a bike an example of a distance or speed multiplier?

### Slow movement of pedals produces a much faster rotation of the wheels

98

## What effort and load do distance multipliers involve?

###
• small movement of effort

• large movement of load

99

## How is energy shown to be conserved in gears?

### Work done by input gear = Work done by output gear

100

## Why can a machine not be a force and distance multiplier at the same time?

### As energy is conserved, if force is doubled the distance is halved and vice versa

101

## What are levers used to do?

### Lift heavy masses with the least amount of effort

102

## What three things can gears do when passing power from one wheel to another?

###
• increase speed - first gear has more teeth than second so second has to turn faster to keep up

• increase force - second gear has more teeth than first so second turns slower but with more force

• change direction - when gears mesh they always turn in the opposite direction

103

## In a hydraulic system, a smaller force on the master (effort) piston will produce what force on the slave (load) piston?

### A larger force as the pressure of the liquid is constant - acting as a force multiplier

104

## What is the ratio of in levers?

### Lengths

105

## What is the ratio of in gears?

### Number of teeth

106

## What is the ratio of in hydraulics?

### Cross sectional areas

107

## Equation for levers?

### Fb/Fa = Lb/La

108

## Equation for gears?

### Fb/Fa = Nb/Na

109

## Equation for hydraulics?

### Fb/Fa = Ab/Aa

110

## What is the atmosphere?

### A thin layer of air around the earth

111

## What happens at a greater altitude?

###
• the less dense the atmosphere

• the lower the atmospheric pressure

112

## Why is the atmospheric pressure lower at greater altitudes?

###
• at higher altitudes there is less air above a surface

• so there is a smaller weight of air acting on the surface

• p=F/A and F is reduced so p will be smaller

113

## How is upthrust created?

### When the bottom surface of an object is submerged in a liquid it experiences a greater pressure than the top surface

114

## When does an object float?

### When its weight = upthrust / weight of fluid displaced

115

## What is upthrust equal to?

### The weight of the liquid displaced

116

## What is the equation for momentum?

### Mass x velocity

117

## What is momentum measured in?

### kgm/s

118

## Why will a ball be harder to stop if it has a large mass and moving at a high speed?

### There will be a greater force exerted on the person's hands by the ball. They will have to exert an equal and opposite force on the ball to stop it

119

## What happens to momentum in a collusion of explosion?

### Momentum is conserved, provided that there are no external forces having an effect

120

## What are the external forces that could have an effect on momentum?

###
• friction which decreases momentum

• gravity (e.g. a collision on a slope)

121