paper 2 : forces Flashcards
(87 cards)
1
Q
what is a scalar quantity
A
a scalar quantity is a measurement with only magnitude(size)
2
Q
what is a vector quantity
A
a vector quantity is a measurement withe magnitude and direction
3
Q
what is a force
A
a force is a push or pull that acts on an object
4
Q
what are some examples of scalar quantities
A
some examples of scalar quantities are :
- speed
- mass
- light intensity
- temperature
- distance
5
Q
what are some examples of vector quantities
A
some examples of vector quantities are:
- velocity
- friction
- momentum
- force
- displacement
6
Q
what is meant by ‘normal contact force’
A
normal contact force is when an object on a flat surface experiences a force perpendicular (at 90 degrees) to the surface
7
Q
what is weight
A
weight is the force acting on an object due to gravity
8
Q
what can cause an objects weight to alter
A
a persons weight can change a]according to the strength of the gravitational field where the object is at
9
Q
how is weight and an objects mass related
A
an objects mass and weight are directly proportional
10
Q
how do you calculate the weight of an object
A
weight = mass x gravitational field strength
W=mg
11
Q
what is weight measured in
A
weight is measured in Newtons (N)
12
Q
what is gravitational field strength measured in
A
gravitational field strength is measured in N/Kg
13
Q
what is a ‘resultant force’
A
a resultant force is a single force that has replaced a number of forces.
a resultant force still has the same effect as all the other forces acting together
14
Q
what is newtons first law
A
newtons first law is : an object in motion will stay in motion at the same velocity until a force is applied
15
Q
when is ‘work done’
A
work is done when a force causes an object to move through a distance
16
Q
how do you calculate work done
A
work done = force x distance(along the line of action of the force)
W=Fs
17
Q
what is one joule of work equivalent to
A
one joule of work is equivalent to when a force of 1 newton causes a displacement of 1m
18
Q
how can you convert joules to newton metres
A
1 joule = 1 newton metre
19
Q
what happens to the temperature of an object when work is done
A
when work done occurs against the frictional forces already acting on an object, the object experiences a temperature increase
20
Q
what is elastic deformation
A
elastic deformation is when an object can return to its original shape and size after all forces applied have been removed
21
Q
what is inelastic deformation
A
inelastic deformation is when an object is unable to return back to its original shape and size, after all forces applied have been removed
22
Q
what is the limit of proportionality
A
the limit of proportionality is the maximum amount of force which can be applied to an object before it is no longer able to return back to its original shape and size
23
Q
how are force and extension related
A
extension is directly proportional to the amount of force applied
24
Q
how do you calculate the force applied to a spring
A
force = spring constant x extension
F=ke
25
how can the calculation for, the force applied to a spring, be adapted when you are given how much a spring has been compressed
when you are given how much a spring has been compressed, you input the difference between the natural length and compressed length, into the 'e' part of F=ke
26
what type of energy transfers occur when a spring in stretched or compressed
when a spring is stretched or compressed, work is done and elastic potential energy is stored in the spring.
27
how are the values for work done on a spring and the elastic potential energy stored in an spring related
the values for work done on a spring and the elastic potential energy stored in an spring are equal, only if the spring is not inelastically deformed
28
how can the work done in stretching or compressing a spring be calculated
the work done in stretching or compressing a spring be calculated using the equation :
Ee=0.5 x k (e)^2
29
what is a turning effect also known as
a turning effect also known as the moment of the force
30
how do you calculate the moment of a force
moment of a force = force x distance (from pivot)
| M=Fd
31
what must happen in order for an object to be balanced (in equilibrium)
in order for an object to be in equilibrium, the total anti clockwise moment must be EQUAL to the total anti-clockwise moment
32
how can you calculate to the total clockwise or anticlockwise turning moments
F1 X d1 = F2 X d2
| force 1 x distance 1 = force 2 x distance 2
33
how do levers affect the force needed to be applied to achieve a certain moment
levers make it easier to do work, as they increase the distance from the pivot meaning that, as M=Fd, LESS force is needed to achieve that same moment
34
how do gears transmit rotational effects
gears can transmit rotational effects as they have 'teeth' which interlock with other gears meaning,if one gear turns one way the other gear will turn in the opposite direction
35
how can pressure at the surface of a fluid be calculated
pressure at the surface of a liquid can be calculated using this equation:
pressure=force normal to a surface/area of that surface (p=F/A)
36
what is meant by a force normal to a surface
if a force is 'normal' to a surface, it just means that it is at a right angle to the surface
37
how can, pressure due to a column of liquid/depth, be calculated
pressure due to a column of liquid be calculated using this equation :
pressure = height of column x density of liquid x gfs
(p=h ρ g)
38
why, in a liquid, does pressure at a point increase as you increase depth/height of the column of liquid above that point
in a liquid, pressure at a point increases as you increase depth/height of the column of liquid above that point, as:
- as we increase depth, we also increase the weight of the liquid above the object
- weight is the force acting on a object due to gravity, and pressure = force/area
- this means that force and pressure are directly proportional as, if the force acting on an object at a certain point increases, pressure must also increase
- therefore increasing our depth,increases the pressure
39
why, in a liquid, does pressure at a point increase as the density of that liquid increases
in a liquid, pressure at a point increases as the density of that liquid increases as :
- if a liquid is more dense, it means there are more particles in a certain area
- if we increase depth, we will also increase the mass of particles above that point, increasing the denisty as ρ=m/V
- if density has increased, pressure must also increase as they are proportional
40
what causes a partially or totally submerged object to experience upthrust
a partially or totally submerged object may experience upthrust if:
- the object experiences a greater force and therefore pressure on the bottom surface, compared to the force and therefore pressure at the top surface
- this creates a resultant force upwards, which is called upthrust
41
how are upthrust and the weight of liquid displaced related
upthrust and the weight of liquid displaced are related because :
-the size of the upthrust acting on the object is the same as the weight of liquid displaced
42
why do some objects float
some objects float because:
- the object is able to displace an amount of liquid that is the equal to the objects weight as it is less dense than the liquid
- this means that force of upthrust will be equal to the weight of the object causing the object to float
43
why do some objects sink
some objects sink because :
-the object is unable to displace enough liquid to equal its own weight as it is denser than the liquid; therefore the weight of the object is greater than the force of upthrust, causing the object to sink
44
what is the atmosphere
the atmosphere is a thin layer of air around the earth which is relative to the earths size.
45
how does the atmosphere change as you increase altitude (height from ground/sea surface)
the atmosphere becomes less dense as you increase altitude
46
how does atmospheric pressure change as height above a surface increases
as height above a surface increases, atmospheric pressure DECREASES because :
- the number of air molecules and therefore weight of air above a surface always decreases as the height above a surface increases.
- if there is less air, the atmospheric pressure will be LOWER as there are less air particles colliding
47
what causes atmospheric pressure
atmospheric pressure is caused by air molecules colliding with a surface
48
what values do you need in order to express displacement
in order to express displacement you need :
- magnitude (size)
- direction
49
what are the typical values for walking,running and cycling
the typical values for running,walking and cycling are :
- walking = 1.5m/s
- running =3m/s
- cycling=6m/s
50
what are the typical values for a car travelling and the speed of sound in air
the typical values for a car travelling and the speed of sound in air are :
- a car travelling = 13m/3
- speed of sound in air = 330m/s
51
how do you calculate distance travelled
disttance travelled = speed x time (s=vt)
52
what is velocity
velocity is the speed of of an object in a certain direction
53
how can, for example, an ice skater be travelling in a circle at a constant speed but at a changing velocity
an ice skater can be travelling in a circle at a constant speed but at a changing velocity as :
-if the ice skater is travelling in a circle, their speed will be constant but as they are going in a circle, their direction is always changing therefore, as velocity is a vector quantity that involves speed and direction, their velocity must also be changing
54
how can the speed of an object be calculated from a distance time graph
the speed of an object be calculated from a distance time graph, by working out the gradient
55
how do you calculate acceleration
you can calculate acceleration using this equation :
| acceleration = change in velocity / time
56
how can acceleration be calculated from a velocity time graph
acceleration can be calculated from a velocity time graph by working out the gradient
57
what is the acceleration of any object, near the earth's surface, falling freely due to gravity
the acceleration of any object, near the earth's surface, falling freely due to gravity is 9.8m/s^2
58
how can uniform acceleration be calculated
uniform acceleration be calculated using the equation :
(final velocity)^2 - (intial velocity)^2 = 2 x acceleration x distance
v^2-u^2 = 2as
59
how can v^2-u^2 = 2as, be arranged to figure out :
- distance
- acceleration
- final velocity
- initial velocity
v^2-u^2 = 2as, can be arranged to figure out :
- distance = (v^2-u^2)/2a
- acceleration = (v^2-u^2)/2s
- final velocity = √2as + u^2
- initial velocity = √2as-v^2
60
what is terminal velocity
terminal velocity is where there is no resultant force meaning that the object moves at a constant speed and direction
61
how is terminal velocity reached
terminal velocity is reached when :
- at the start, the object accelerates downwards due to the force of gravity
- as the object's speed increases, frictional forces such as air resistance or drag increase
- eventually the weight of the object due to gravity is balanced by the frictional forces, and the resultant force is zero (terminal velocity)
62
what is inertia
inertia is the tendency for objects to continue in their state of rest or uniform motion
63
what is newtons second law
newtons second law is : acceleration is proportional to the resultant force, but inversely proportional to the mass of the object
64
what equation is linked to newtons second law
the equation linked to newtons second law is :
| F=ma
65
what is inertial mass
inertial mass is the measure of how difficult it is to change the velocity of an object and is also the ratio of force over acceleration
66
what is newtons third law
newtons third law is : whenever two objects interact, the forces that they exert on each other are equal and opposite
67
what does it mean for two forces to be 'equal but opposite'
if two forces are equal but opposite, it means that the magnitude of the forces are the same but their directions are different
68
what is the normal contact force also equal to
normal contact force is the same as an objects weight
69
what is the stopping distance of a vehicle
the stopping distance of a vehicle is the sum of the thinking distance and the braking distance
70
what is the thinking distance
the thinking distance is the distance the vehicle travels during the drivers reaction time
71
what is the braking distance
the braking distance is the distance the vehicle travels between the time when the driver applies the brakes and when the vehicle actually stops
72
what factors affect the thinking distance
factors which affect thinking distance are :
- intoxication(drugs and alcohol)
- visibility
- distractions
- tiredness
73
what factors affect the braking distance
factors which affect braking distance are :
- velocity
- icy roads
- brake wear
- wet roads
74
on a velocity time graph what does a straight line mean
on a velocity time graph a straight line means that the object is travelling at a constant rate
75
what is the typical value for human reaction time
the typical value for human reaction time ranges from 0.2s to 0.9s
76
how do the following affect braking distance and total stopping distance :
- brake wear
- wet/icy roads
- velocity of vehicle
the following affect braking distance and total stopping distance as :
- if the BRAKES have been WORN out, there will be a decrease in the braking force applied, meaning that it will take longer for the vehicle to stop
- if the roads are WET/ICY, there is reduced friction meaning that the braking force applied will be lower and it will take longer for the car to stop
- if the VELOCITY of the vehicle is high, it will require a greater braking force and it will also take longer for the car to stop
77
why is it dangerous to be very close to other vehicles when the roads are icy/wet
it is dangerous to be very closer to other vehicles when the roads are icy/wet, as icy/wet roads increase stopping distance so if the space between vehicles is very small, there may be a crash
78
why are large decelerations dangerous
large decelerations are dangerous because :
| they can cause the breaks to overheat or loss of control may occur
79
why do large decelerations lead to the brakes overheating or loss of control
large decelerations can cause brake overhearing or loss of control as :
- work done occurs between the brakes and wheel when a force is applied to the brakes
- this causes there to be an energy transfer from the kinetic store ,to the temperature store in the brakes
- the greater the speed of the vehicle, the greater the braking force must be which results in a greater deceleration of the vehicle
80
how can the forces involved in the deceleration of road vehicles be estimated
the forces involved in the deceleration of road vehicles be estimated using the following equation :
force = mass x acceleration (F=ma)
81
how can momentum be calculated
momentum can be calculated using this equation :
| momentum = mass x velocity
82
what is the law of the conservation of momentum
the law of the conservation of momentum is :
| -in a closed system, the total momentum before an event is equal to the total momentum after an event
83
what happens to an object momentum when a force is applied
when a force is applied to an object that is moving, a change in momentum occurs
84
how can the force applied to the object, which caused the change in momentum be calculated
the force applied to an object, which caused a change in momentum be calculated using this equation :
force=change in momentum / time
85
what 2 equations have been combined to give the equation for the force which causes a change in momentum
the 2 equations which have been combined to find out the force which causes a change in momentum are :
F=ma and change in velocity/t
86
what is the force, that causes a change in momentum
the force, that causes a change in momentum, is simply the rate of change of momentum
87
how do safety features like air bags,seat belts,crash mats cycle helmets etc, work in relation to the concept of rate of change of momentum
safety features like air bags,seat belts,crash mats cycle helmets etc, to reduce the rate of change of momentum by :
- the safety feature increases the time taken for the person/object to stop
- this reduces the rate of change of momentum
- which reduces the force applied to the person/object upon landing
