Forces Flashcards
1
Q
what are forces
A
interactions between two objects that can be a push or a pull
2
Q
what does a scalar quantity have
A
a magnitude and no direction
3
Q
what does a vector quantity ahve
A
magnitude and an associated direction
4
Q
how are vector quantities represented
A
by an arrow
5
Q
what does the length of a vector arrrow represent
A
the magnitude
6
Q
what does the direction of a vector arrow represent
A
the direction of the vector quantity
7
Q
what does a contact force mean
A
the objects are physically touching
8
Q
what does a non contact force mean
A
the objects are physically separated
9
Q
examples of scalar quantities
A
mass
volume
10
Q
examples of vector quantities
A
acceleration
force
11
Q
examples of contact forces
A
friction
air resistance
tension
reaction force
12
Q
examples of non contact forces
A
gravitational force
electrostatic force
magnetic force
13
Q
what is weight
A
the force acting on an object due to gravity. the force of the gravity close to the earth is due to the gravitational field around the earth.
14
Q
what does gravity effect
A
all things with mass
15
Q
what does the weight of an object depend on
A
the gravitational field strength at the point where the object is
16
Q
what is the equation for weight
A
weight = mass x gravity
17
Q
what is weight measured in
A
N
18
Q
what is gravitational field strength measured in
A
N/Kg
19
Q
what is the link between weight and mass of an object
A
directly proportional
20
Q
how is weight measured
A
calibrated spring balance (newton meter)
21
Q
what is the resultant force
A
a single force that replaces a number of forces acting on an object but has the same effect as all the original forces acting together
22
Q
what is newtons 1st law
A
if forces acting on an object are balanced then it will
be stationary
or be moving at a constant speed
23
Q
when is work done on an object
A
when a force causes an object to move through a distance
24
Q
why is an object displaced when a force is applied
A
it has done work
25
work done equation
force x distance
26
when is one joule of work done
when a force of one newton causes a displacement of one metre
27
what does one joule equal
one newton metre
28
what does work done against the frictional forces acting on an object cause
a rise in the temperature of the object
29
what is newtons 3rd law
forces normally act in pairs because two objects that interact with each other exert equal and opposite forces on eachother
30
what is the centre of mass of an object
the point at which its mass can be thought to be concentrated
31
where is the centre of mass of a regular shape found
where two lines of symmetry meet
32
when is an object in equilibrium
when the object is suspended
33
conditions for an object to be stable
the line of action of the force acts within the objects base
34
what is a pívot
a point at which a lever can rotate
35
what is a load
an object that moves
36
what is effort
force required to move the load
37
what is a lever
anything that can turn
levers are simple machines that can act as force multipliers
38
what causes a moment
because of the pívot point an applied force can cause a turning effect
39
units of a moment
newton metres or newton cm
40
what is the distance in the moment equation
perpendicular distance from the pívot to the line of action of the force
41
what causes a lever to be in equilibrium
the sum of the clockwise moments must be equal to the sum of anticlockwise moments
42
typical speed of a person walking
1.5m/s
43
typical speed of a person running
3m/s
44
typical speed of someone cycling
6m/s
45
typical value of speed of sound in air
330m/s
46
what does the speed a person can walk run or cycle depend on
age, terrain, fitness, distance travelled
47
what do gears act as
a force multiplier
48
what does a low gear cause
low speed and a high turning effect
49
what does a high gear give
high speed and a low turning effect
50
how do you calculate speed
distance / time
51
unit of speed
m/s
52
what is velocity
an objects speed in a given direction
53
how can two objects have the same speed but different velocities
they travel in opposite directions
54
what happens if an object moves at a constant speed in a circle
its velocity is constantly changing even though its speed is constant
55
how can the distance travelled be presented if an object moves along a straight line
a distance time graph
56
what is acceleration
the change in velocity per second
57
acceleration calculation
change in velocity / time taken
58
acceleration units
m/s^2
59
what is deceleration
when an object is slowing down
60
constant acceleration equation
(final velocity)^2 - (initial velocity)^2 = 2 x acceleration x distance
61
what is the acceleration of any object falling freely under gravity near the earths surface
9.8m/s^2
62
why does an object falling through a fluid initially accelerate
the force of gravity
63
what do distance time graphs show
how an objects distance varies within time
64
where is time always plotted on a dt graph
x axis
65
what is the gradient of a distance time graph
the speed
66
what does a velocity time graph show
how the velocity of an object is changing with time
67
what does the gradient of a velocity time graph show
the acceleration or deceleration of the object
68
what does the area under a velocity time graph show
the distance travelled by the object
69
what kind of quantity is distance
scalar
70
what kind of quantity is speed
scalar quantity
71
what kind of quantity is velocity
vector quantity
72
what does displacement include
the distance an object moves and the direction of that straight line
73
what kind of quantity is displacement
vector quantity
74
what is newton's second law
the acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object
75
what can a fluid be
a liquid or a gas
76
what does pressure in fluids cause
a force normal (at right ángles) to any surface
77
pressure at the surface of a fluid equation
force normal to a surface / area of that surface
78
what is pressure measured in
Pa
79
equation for pressure due to a column of liquid
height of the column x density of the liquid x gravitational field strenth
80
where is the atmosphere most dense
the surface of the earth
81
when does the atmosphere get less dense
when the altitude increases
82
what happens as a surface increases height above ground level
the number of air molecules above the surface decreases
83
what causes an object to inflate
when the air pressure outside of it is lower than the pressure inside of the object
84
why does a partially or fully submerged object experience
a greater pressure on the bottom surface than on the top surface which created upthrust
85
what creates atmospheric pressure
air molecules colliding with a surface
86
how does depth affect pressure in a liquid
increases pressure
87
why does a greater depth increase pressure
there is a greater weight of liquid acting downwards
88
how does density affect pressure in a liquid
increases pressure
89
what needs to happen for an object to float
the upthrust must equal the objects weight
90
when does an object sink
if the upthrust is less than the objects weight
91
what is the size of the upthrust acting on the object the same as
the weight of water displaced by the object
92
what is the equation for force (2nd law)
force = mass x acceleration
93
what is inertia
the tendency of an object to stay at rest or continue to move in a uniform motion
94
what is the inertia of an object dependent on
its mass
95
what is the stopping distance of a vehicle
the sum of the distance the vehicle travels during the drivers reaction time and the distance it travels under the braking force
96
what is the thinking distance
the distance travelled by the vehicle during the drivers reaction time
97
what is the braking distance
the distance travelled by the vehicle while the braking force is being applied
98
what factors affect braking distance
road surface
speed
road conditions
mass of car
condition of tyres
condition of brakes
99
what factors affect thinking distance
alcohol
tiredness
speed
age
visibility
drugs
distractions
100
what are typical reaction times in humans
0.2s to 0.9s
101
what can be caused by braking too fast
kinetic energy converted to thermal
can cause brakes to overheat
driver loses control of vehicle
102
what is momentum
when a force acts on a body that is moving or able to move a change in momentum occurs
103
what does momentum have
magnitude and direction
104
momentum equation
mass x velocity
105
momentum in a closed system
total momentum before an event is equal to the total momentum after the event
106
what happens to momentum during a car crash
momentum of the passenger falls from a large amount to zero in less than a second
107
what is an impact force
the force created when a change in momentum occurs
108
impact force equation
change in momentum/ impact time
109
what do rapid changes in momentum cause
huge dangerous forces being applied
110
how can danger of impact forces be reduced
make change in momentum happen over a longer time
111
what equipment can slow down momentum change
airbags
seatbelts
crashmat
bike helmet
cushioned surface
112
how do safety features slow down momentum change
reduce forces acting which reduces risk of injury
