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*AQA GCSE Physics* > 5. Forces > Flashcards

5. Forces Flashcards

1
Q

What is a scalar?

A

Quantities that are fully described by magnitude or size

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2
Q

What are vectors?

A

Quantities that are fully described by both a magnitude and direction

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3
Q

What is distance?

A

A scalar quantity that refers to ‘how much ground an object has covered’

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4
Q

What is displacement?

A

A vector quantity that refers to ‘how far out of place an object is’

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5
Q

What is magnitude?

A

Size

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6
Q

How can vectors be drawn?

A

Using arrows

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7
Q

Is time a vector or scalar quantity?

A

scalar

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8
Q

Is force a vector or scalar quantity?

A

Vector

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9
Q

Is friction a vector or scalar quantity?

A

Vector

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10
Q

Is weight a vector or scalar quantity?

A

Vector

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11
Q

Is displacement a vector or scalar quantity?

A

Vector

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12
Q

Is distance a vector or scalar quantity?

A

Scalar

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13
Q

Is density a vector or scalar quantity?

A

Scalar

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14
Q

Is energy a vector or scalar quantity?

A

Scalar

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15
Q

Is frequency a vector or scalar quantity?

A

Scalar

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16
Q

Is mass a vector or scalar quantity?

A

Scalar

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17
Q

Is power a vector or scalar quantity?

A

Scalar

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18
Q

Is voltage a vector or scalar quantity?

A

Scalar

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19
Q

Is volume a vector or scalar quantity?

A

Scalar

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20
Q

What is the gradient on a distance-time graph?

A

Velocity

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21
Q

What is the gradient on a velocity-time graph?

A

Acceleration

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22
Q

What is the area under a velocity-time graph?

A

The distance

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23
Q

What is acceleration?

A

When an object speeds up or changes direction

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24
Q

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

A

The total distance travelled

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25
Q

What is the unit of force?

A

Newtons, N

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26
Q

Examples of contact forces?

A
  • Friction
  • Air / Water resistance (drag)
  • Normal contact (reaction)
  • Tension
  • Upthrust
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27
Q

Examples of non-contact forces?

A
  • Gravity
  • Magnetic
  • Electrostatic
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28
Q

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

A

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

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29
Q

What is enersher?

A

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

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30
Q

What is Newton’s 1st law of motion?

A

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

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31
Q

What is Newton’s 2nd law of motion?

A

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

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32
Q

What equation shows Newtons 2nd law of motion?

A

F = m a

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33
Q

What is Newton’s 3rd law of motion?

A

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

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34
Q

How is inertial mass defined?

A

By the ratio of force over acceleration

if an object is more inert then it’s harder to move

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35
Q

What is thinking distance proportional to?

A

Speed

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36
Q

What is braking distance proportional to?

A

Speed2

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37
Q

What is thinking distance?

A

The distance travelled during reaction time.

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38
Q

What is braking distance?

A

The distance travelled while the brakes are applied.

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39
Q

Why does thinking distance increase?

A
  • the speed increases

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

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40
Q

When does braking distance increase?

A

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

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41
Q

How is thinking distance decreased?

A

Friction reduced - wet roads, worn tyres or brakes

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42
Q

How is braking distance decreased?

A

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

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43
Q

How is thinking distance shown on a graph?

A

Area of the rectangle underneath the graph

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44
Q

How is braking distance shown on a graph?

A

Area of the triangle underneath the graph

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45
Q

Typical speed of walking?

A

1.5 m/s

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46
Q

Typical speed of running?

A

12 m/s

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47
Q

Typical speed of driving?

A

20 m/s

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48
Q

Typical speed of flying?

A

200 m/s

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49
Q

Speed of sound in air?

A

3x10 squared

50
Q

Speed of light?

A

3x10 to the 8

51
Q

What is the weight of an object?

A

The force of gravity on it

52
Q

How to convert from Kg to N?

A

x10

53
Q

When does an object reach constant velocity?

A

When the drag force is equal and opposite to its weight

54
Q

What is terminal velocity?

A

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

55
Q

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

A

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

56
Q

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

A

It is equal to zero

57
Q

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

A

The resultant force is equal to its weight, initally

58
Q

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

A

10 m/s2

59
Q

What are plastic objects?

A

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

60
Q

What are elastic objects?

A

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
Q

Does an elastic collision lose kinetic energy?

A

No

62
Q

What does Hooke’s law state?

A

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

63
Q

What is the spring extension?

A

New length - original length

64
Q

What does hooke’s law only apply to?

A

Elastic materials

65
Q

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

A

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

66
Q

What is elastic limit?

A

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

67
Q

What is stopping distance?

A

Thinking distance + braking distance

68
Q

What are the two SUVAT equations?

A

v = u + at

v2 = u2 - 2as

69
Q

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

A
  • increase the size of the force

* increase the distance from the pivot

70
Q

What is the turning effect of a force called?

A

A moment

71
Q

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

A

M=Fd

72
Q

What are moments measured in?

A

Nm

73
Q

When will a seesaw balance in terms of moments?

A

When the anticlockwise moment is equal to the clockwise one

74
Q

What does the principle of moments state?

A

For a balanced object, clockwise moments = anticlockwise moments

75
Q

What is the centre of mass of an object?

A

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

76
Q

Where does the centre of mass lie in symmetrical objects?

A

Along the line of symmetry

77
Q

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

A

Where the lines of symmetry intersect

78
Q

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

A

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

79
Q

How can the COM of an irregular shape be found?

A
  • 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
Q

What is the stability of an object affected by?

A
  • the width of the base of the object

* the height of it’s centre of mass

81
Q

When will an object not topple over?

A

When the line of action is within the base

82
Q

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

A
  • stable equilibrium - tilts and falls back to original position
  • unstable equilibrium - tilts and falls
  • neutral equilibrium - rolls
83
Q

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

A

It is raised

84
Q

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

A

It is lowered

85
Q

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

A

It stays at the same level if pushed

86
Q

What does the pressure of a liquid depend on?

A

The depth and the density

87
Q

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

A

pressure = depth x field strength x density

88
Q

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

A

The pressure acts in all directions and is the same depth

89
Q

What is the nature of liquid pressures at different depths?

A

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

90
Q

What is a gear?

A

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

91
Q

What do gears act as?

A

A force multiplier

92
Q

What is a force multiplier?

A

Machines designed to increase the size of the force

93
Q

What is a distance multiplier?

A

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

94
Q

What effort and load do force multipliers involve?

A
  • small effort (input force)

* larger load (output force)

95
Q

Equation for mechanical advantage?

A

load / effort

96
Q

Example of a force multiplier?

A

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

97
Q

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

A

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

98
Q

What effort and load do distance multipliers involve?

A
  • small movement of effort

* large movement of load

99
Q

How is energy shown to be conserved in gears?

A

Work done by input gear = Work done by output gear

100
Q

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

A

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

101
Q

What are levers used to do?

A

Lift heavy masses with the least amount of effort

102
Q

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

A
  • 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
Q

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

A

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

104
Q

What is the ratio of in levers?

A

Lengths

105
Q

What is the ratio of in gears?

A

Number of teeth

106
Q

What is the ratio of in hydraulics?

A

Cross sectional areas

107
Q

Equation for levers?

A

Fb/Fa = Lb/La

108
Q

Equation for gears?

A

Fb/Fa = Nb/Na

109
Q

Equation for hydraulics?

A

Fb/Fa = Ab/Aa

110
Q

What is the atmosphere?

A

A thin layer of air around the earth

111
Q

What happens at a greater altitude?

A
  • the less dense the atmosphere

* the lower the atmospheric pressure

112
Q

Why is the atmospheric pressure lower at greater altitudes?

A
  • 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
Q

How is upthrust created?

A

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

114
Q

When does an object float?

A

When its weight = upthrust / weight of fluid displaced

115
Q

What is upthrust equal to?

A

The weight of the liquid displaced

116
Q

What is the equation for momentum?

A

Mass x velocity

117
Q

What is momentum measured in?

A

kgm/s

118
Q

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

A

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
Q

What happens to momentum in a collusion of explosion?

A

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

120
Q

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

A
  • friction which decreases momentum

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

121
Q

What does force equal in terms of the change in momentum?

A

Force = change in momentum / time taken

*AQA GCSE Physics* (10 decks)

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