Forces Flashcards
(119 cards)
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
Inelastically deformed
Object does not return to its original shape after force is applied
26
The extension of an elastic object is directly proportional to
The applied force
27
Once the limit of proportionality has been exceeded:
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
Equation which applies to the linear section of a force extension graph
and to the compression of an elastic object
Force = spring constant x extension
29
Spring constant indicates
How easy it is to stretch or compress a spring
Higher it is the stiffer the spring is
30
A force that stretches or compresses a spring contains
Elastic potential energy
31
The amount of energy done and the work stored are
Equal providing the spring does not go past the limit of proportionality
32
Required practical
Pg11
33
When a force causes an object to rotate about a pivot
The turning effect is called a moment of a force
34
Moment of a force equation
Force x distance
35
If an object is balance, the total clockwise moment about the pivot equals
The total anti-clockwise moment about that pivot
F1xd1=f2xd2
36
What increases when the applied force moves further than the transmitted force
The force
37
What increases when the applied force is bigger than the transmitted force
The distance
38
A fluid
Liquid or gas
39
Particles in a fluid
Collide with the surface of objects or container
40
Pressure equation
Force normal to surface /
| Area of that surface
41
If the pressure acts on a bigger area
It will produce a larger force
42
The atmosphere is
A relatively thin layer of air around the earth
43
The greater the altitude
The less dense the atmosphere and the lower the atmospheric pressure
44
At high altitude
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
Résultant force
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
A free body diagram can be used to show
Different forces acting on an object
47
Scale vector diagrams are used to illustrate the overall effect when more than one force acts on an object
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
Scale vector diagrams can also be used when a force is acting in a diagonal direction
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
When a force causes an object to move
Work is done on the object
| This is because it requires energy to move the object
50
One joule of work is done when
One Newton is moved one metre
51
Work done formula
Work done= force x distance
52
When work is done
Energy transfers take place within the system
53
To change the shape of an object
More than one force much be applied
54
Elastically deformed =
If an object returns to its original shape after forces are applied
55
Inelastically deformed
Object does not return to its original shape after force is applied
56
The extension of an elastic object is directly proportional to
The applied force
57
Once the limit of proportionality has been exceeded:
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
Equation which applies to the linear section of a force extension graph
and to the compression of an elastic object
Force = spring constant x extension
59
Spring constant indicates
How easy it is to stretch or compress a spring
Higher it is the stiffer the spring is
60
A force that stretches or compresses a spring contains
Elastic potential energy
61
The amount of energy done and the work stored are
Equal providing the spring does not go past the limit of proportionality
62
Pressure at a particular point in a column of liquid depends on
The height of the column above the point
| The density of the liquid
63
The higher the column and the more dense the liquid
The greater the weight above the point
The greater the force on the surface at that point
The greater the pressure
64
Pressure equation
Height of the column X density of the liquid X gravitational field strength
65
When an object is submerged in a liquid
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
Upthrust is
The upward force exerted by fluid on the submerged object
67
Object floats when
Its weight is equal to the upthrust
68
And object sinks when
Its weight is greater than the upthrust
69
Weather and object will float or sink depends on
The density
70
If an object is less dense than the liquid
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
If an object has a low-density
More of the object will remain above the surface
72
Size of upthrust it’s always equal to
The weight of liquid displaced
73
An object denser then the surrounding liquid cannot
Displace enough liquid to equal its own weight so it sinks
74
Distance
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
Displacement
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
Speed measure
How fast something is going
Scalar quantity
M/s
77
Distance =
Speed x time
78
Velocity is
Vector
Speed of am object In a given direction
79
When travelling in a straight line and object with constant speed also has
Constant velocity
80
If an object is not travelling in a straight line
The speed can still be constant but the velocity will change because the direction has changed
81
object moving in a circle
Constantly changing direction so constantly changing velocity it is accelerating even if it is at a constant speed
Eg orbiting planets
82
Newton’s first law
An object will remain in the same state of motion unless acted on by an external force
83
When the resultant force is zero
Remains stationary if already
If moving stays at a constant velocity
This is called inertia
84
Velocity only changes if
Theee is a resultant force
85
Distance time graph represents
The motion of an object travelling in a straight line
86
Gradient of a distance time graph shows
Speed
87
Distance time graph is a curve if
It is accelerating
Tangent to figure it out
88
Acceleration is
How quickly something speeds up slows down or changes direction
89
Acceleration equation
Acceleration =
Change in velocity /
Time taken
90
Acceleration is negative when
An object slows down
91
Uniform acceleration equation
Final velocity^2 —initial velocity ^2=
2 x acceleration X distance
92
Gradient of a velocity time graph
Acceleration
93
Area under at velocity time graph
distance
94
Newtons second law
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
Newtons law equation second
Force = mass X acceleration
96
Mass is a measure of
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
Required practical
Pg 17
98
When an object falls through a fluid
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
Acceleration near the earths surface is
10m/s^2
Due to gravity
100
Newton’s third law is
For every action there is an equal and opposite reaction
101
When one object exerts a force on another
The other object exerts a force back
Same type and equal in size but opposite in direction
102
Momentum equation
Mass x Velocity
103
A change in momentum occurs when
Unbalanced force acts on an object that is moving or able to move
104
Change in momentum equation
Force =Change of momentum/changing time
105
Safety devices reduce
The forced by increasing the time over which change in the momentum takes place
106
In a closed system the total momentum before and event is equal to
Total momentum After an event
Most often referred to during collisions
107
The stopping distance of a vehicle depends on
The thinking distance and the braking distance
108
For a given braking distance
The greater the speed of the vehicle the longer the stopping distance
109
Thinking distance is directly proportional to
Speed
110
If you double the speed the braking distance increases
By a Factor of four
111
Reaction times for humans
0.2-0.9 seconds
112
Reaction time can be affected by
Tiredness, drugs, alcohol, distractions
113
Braking distance can be affected bye
Condition of road, the vehicle, the weather
Wet or icy
Worn brakes and tyres and over inflated or underinflated tires
114
The greater the braking force
The greater the deceleration
115
To stop the vehicle
Breaks need to apply force to the wheels
116
Temperature of brakes increases by
Work done that by frictional force transfering kinetic energy to heat energy
117
If the braking force is to large
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
Find the size of breaking force equation
Work done (kinetic energy) = force X distance (breaking distance)
119
For a given braking distance
Doubling the mass doubles the force required
| Doubling the speed quadruples the force required
