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Flashcards in Forces Deck (119)
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1
Q

Scalar quantities have

A

Magnitude only (size)

2
Q

A vector quantity has

A

Magnitude and direction

3
Q

Represent vector quantities using

A

Arrows

Length shows the magnitude
Points in the direction that the vector quantity is acting

4
Q

Forces are …….. quantities

A

Vector

5
Q

A force occurs when

A

Two or more objects interact

6
Q

Forces are either

A

Contact so objects are touching

Non contact so objects are not touching

7
Q

Example of contact forces

A
Friction 
Air resistance/drag
Tension
Normal contact force
Upthrust
8
Q

Examples of non contact forces

A

Gravitational force
Electrostatic force
Magnetic force

9
Q

Gravity is

A

A force of attraction between all masses

10
Q

The force of gravity close to earth is due to the

A

Gravitational field around the planet

11
Q

The mass of an object is related to the

A

Amount of matter it contains and is constant

12
Q

Weight is

A

The force acting on an object due to gravity

13
Q

The weight of an object depend on

A

The gravitational field strength where the object is and is directly proportional to its mass

14
Q

Formula for weight

A

Weight =

mass x gravitational field strength

15
Q

Résultant force

A

When more than one force acts on an object These forces can be seen as a single force that has the same effect as all the forces acting togerh r

16
Q

A free body diagram can be used to show

A

Different forces acting on an object

17
Q

Scale vector diagrams are used to illustrate the overall effect when more than one force acts on an object

A

The forces are added together to find a single resultant force, including both magnitude and direction
The vectors are added head to tail and a resultant force arrow is drawn

18
Q

Scale vector diagrams can also be used when a force is acting in a diagonal direction

A

Expressing the diagonal force as two forces at right angles to each other can help work out what effect the force will have
The force F(r) can be broken into F(1) and F(2)
F(1) is the same length of F(r) in the horizontal direction
F(2) is th same length of F(r) in the horizontal direction

19
Q

When a force causes an object to move

A

Work is done on the object

This is because it requires energy to move the object

20
Q

One joule of work is done when

A

One Newton is moved one metre

21
Q

Work done formula

A

Work done= force x distance

22
Q

When work is done

A

Energy transfers take place within the system

23
Q

To change the shape of an object

A

More than one force much be applied

24
Q

Elastically deformed =

A

If an object returns to its original shape after forces are applied

25
Q

Inelastically deformed

A

Object does not return to its original shape after force is applied

26
Q

The extension of an elastic object is directly proportional to

A

The applied force

27
Q

Once the limit of proportionality has been exceeded:

A

Doubling the force will no longer exactly double the extension
The relationship become non linear
A force-extension graph will stop being a straight line

28
Q

Equation which applies to the linear section of a force extension graph

and to the compression of an elastic object

A

Force = spring constant x extension

29
Q

Spring constant indicates

A

How easy it is to stretch or compress a spring

Higher it is the stiffer the spring is

30
Q

A force that stretches or compresses a spring contains

A

Elastic potential energy

31
Q

The amount of energy done and the work stored are

A

Equal providing the spring does not go past the limit of proportionality

32
Q

Required practical

A

Pg11

33
Q

When a force causes an object to rotate about a pivot

A

The turning effect is called a moment of a force

34
Q

Moment of a force equation

A

Force x distance

35
Q

If an object is balance, the total clockwise moment about the pivot equals

A

The total anti-clockwise moment about that pivot

F1xd1=f2xd2

36
Q

What increases when the applied force moves further than the transmitted force

A

The force

37
Q

What increases when the applied force is bigger than the transmitted force

A

The distance

38
Q

A fluid

A

Liquid or gas

39
Q

Particles in a fluid

A

Collide with the surface of objects or container

40
Q

Pressure equation

A

Force normal to surface /

Area of that surface

41
Q

If the pressure acts on a bigger area

A

It will produce a larger force

42
Q

The atmosphere is

A

A relatively thin layer of air around the earth

43
Q

The greater the altitude

A

The less dense the atmosphere and the lower the atmospheric pressure

44
Q

At high altitude

A

There is less air above a surface than at lower altitudes, so there is a smaller weight of air acting on the surface and the equation
P=f/a will result in a lower pressure

45
Q

Résultant force

A

When more than one force acts on an object These forces can be seen as a single force that has the same effect as all the forces acting togerh r

46
Q

A free body diagram can be used to show

A

Different forces acting on an object

47
Q

Scale vector diagrams are used to illustrate the overall effect when more than one force acts on an object

A

The forces are added together to find a single resultant force, including both magnitude and direction
The vectors are added head to tail and a resultant force arrow is drawn

48
Q

Scale vector diagrams can also be used when a force is acting in a diagonal direction

A

Expressing the diagonal force as two forces at right angles to each other can help work out what effect the force will have
The force F(r) can be broken into F(1) and F(2)
F(1) is the same length of F(r) in the horizontal direction
F(2) is th same length of F(r) in the horizontal direction

49
Q

When a force causes an object to move

A

Work is done on the object

This is because it requires energy to move the object

50
Q

One joule of work is done when

A

One Newton is moved one metre

51
Q

Work done formula

A

Work done= force x distance

52
Q

When work is done

A

Energy transfers take place within the system

53
Q

To change the shape of an object

A

More than one force much be applied

54
Q

Elastically deformed =

A

If an object returns to its original shape after forces are applied

55
Q

Inelastically deformed

A

Object does not return to its original shape after force is applied

56
Q

The extension of an elastic object is directly proportional to

A

The applied force

57
Q

Once the limit of proportionality has been exceeded:

A

Doubling the force will no longer exactly double the extension
The relationship become non linear
A force-extension graph will stop being a straight line

58
Q

Equation which applies to the linear section of a force extension graph

and to the compression of an elastic object

A

Force = spring constant x extension

59
Q

Spring constant indicates

A

How easy it is to stretch or compress a spring

Higher it is the stiffer the spring is

60
Q

A force that stretches or compresses a spring contains

A

Elastic potential energy

61
Q

The amount of energy done and the work stored are

A

Equal providing the spring does not go past the limit of proportionality

62
Q

Pressure at a particular point in a column of liquid depends on

A

The height of the column above the point

The density of the liquid

63
Q

The higher the column and the more dense the liquid

A

The greater the weight above the point
The greater the force on the surface at that point
The greater the pressure

64
Q

Pressure equation

A

Height of the column X density of the liquid X gravitational field strength

65
Q

When an object is submerged in a liquid

A

There is a greater height of liquid above the bottom surface than above the top surface

The bottom surface of experiences a greater pressure than the top surface and this creates a resultant force upwards

66
Q

Upthrust is

A

The upward force exerted by fluid on the submerged object

67
Q

Object floats when

A

Its weight is equal to the upthrust

68
Q

And object sinks when

A

Its weight is greater than the upthrust

69
Q

Weather and object will float or sink depends on

A

The density

70
Q

If an object is less dense than the liquid

A

Displaces volume of liquid greater than its own weight so it will rise to the surface

Will float with some of the objects remaining below surface

Displaces liquid of equal weight to the object

71
Q

If an object has a low-density

A

More of the object will remain above the surface

72
Q

Size of upthrust it’s always equal to

A

The weight of liquid displaced

73
Q

An object denser then the surrounding liquid cannot

A

Displace enough liquid to equal its own weight so it sinks

74
Q

Distance

A

Scalar quantity
How far and object moves
Does not take into account the direction and object is travelling in or even if it ends up back where it started

75
Q

Displacement

A

It has a magnitude, which describes how far the object has travelled from the original in a straight line
It has direction which is the direction of the straight line
Vector quantity

76
Q

Speed measure

A

How fast something is going

Scalar quantity

M/s

77
Q

Distance =

A

Speed x time

78
Q

Velocity is

A

Vector

Speed of am object In a given direction

79
Q

When travelling in a straight line and object with constant speed also has

A

Constant velocity

80
Q

If an object is not travelling in a straight line

A

The speed can still be constant but the velocity will change because the direction has changed

81
Q

object moving in a circle

A

Constantly changing direction so constantly changing velocity it is accelerating even if it is at a constant speed

Eg orbiting planets

82
Q

Newton’s first law

A

An object will remain in the same state of motion unless acted on by an external force

83
Q

When the resultant force is zero

A

Remains stationary if already
If moving stays at a constant velocity
This is called inertia

84
Q

Velocity only changes if

A

Theee is a resultant force

85
Q

Distance time graph represents

A

The motion of an object travelling in a straight line

86
Q

Gradient of a distance time graph shows

A

Speed

87
Q

Distance time graph is a curve if

A

It is accelerating

Tangent to figure it out

88
Q

Acceleration is

A

How quickly something speeds up slows down or changes direction

89
Q

Acceleration equation

A

Acceleration =

Change in velocity /
Time taken

90
Q

Acceleration is negative when

A

An object slows down

91
Q

Uniform acceleration equation

A

Final velocity^2 —initial velocity ^2=

2 x acceleration X distance

92
Q

Gradient of a velocity time graph

A

Acceleration

93
Q

Area under at velocity time graph

A

distance

94
Q

Newtons second law

A

The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to to the mass of the object

If the resultant force is doubled the acceleration will be doubled
If the mass is doubled the acceleration will be halved

95
Q

Newtons law equation second

A

Force = mass X acceleration

96
Q

Mass is a measure of

A

Inertia

It describes how difficult it is to change the velocity of an object this inertial mass is given by the ratio of force over acceleration the larger the mass the bigger the force needed to change the velocity

97
Q

Required practical

A

Pg 17

98
Q

When an object falls through a fluid

A

At first the object accelerates due to the force of gravity
As it speeds up the resistive forces increase
The resultant force reaches zero when the resistive forces balance the force of gravity. At this point the object will fall at the steady speed called terminal velocity

99
Q

Acceleration near the earths surface is

A

10m/s^2

Due to gravity

100
Q

Newton’s third law is

A

For every action there is an equal and opposite reaction

101
Q

When one object exerts a force on another

A

The other object exerts a force back

Same type and equal in size but opposite in direction

102
Q

Momentum equation

A

Mass x Velocity

103
Q

A change in momentum occurs when

A

Unbalanced force acts on an object that is moving or able to move

104
Q

Change in momentum equation

A

Force =Change of momentum/changing time

105
Q

Safety devices reduce

A

The forced by increasing the time over which change in the momentum takes place

106
Q

In a closed system the total momentum before and event is equal to

A

Total momentum After an event

Most often referred to during collisions

107
Q

The stopping distance of a vehicle depends on

A

The thinking distance and the braking distance

108
Q

For a given braking distance

A

The greater the speed of the vehicle the longer the stopping distance

109
Q

Thinking distance is directly proportional to

A

Speed

110
Q

If you double the speed the braking distance increases

A

By a Factor of four

111
Q

Reaction times for humans

A

0.2-0.9 seconds

112
Q

Reaction time can be affected by

A

Tiredness, drugs, alcohol, distractions

113
Q

Braking distance can be affected bye

A

Condition of road, the vehicle, the weather
Wet or icy
Worn brakes and tyres and over inflated or underinflated tires

114
Q

The greater the braking force

A

The greater the deceleration

115
Q

To stop the vehicle

A

Breaks need to apply force to the wheels

116
Q

Temperature of brakes increases by

A

Work done that by frictional force transfering kinetic energy to heat energy

117
Q

If the braking force is to large

A

The brakes might overheat all the tires May lose traction on the road resulting in skidding

More likely if tires and brakes are in poor conditions

118
Q

Find the size of breaking force equation

A

Work done (kinetic energy) = force X distance (breaking distance)

119
Q

For a given braking distance

A

Doubling the mass doubles the force required

Doubling the speed quadruples the force required