forces Flashcards
(94 cards)
1
Q
what are scalers
A
physical quantities that only have a magnitude (size)
2
Q
what are some examples of scalars
A
- speed
- distance
- mass
- temperature
- time
3
Q
what are vectors
A
quantities with both magnitude and direction
4
Q
what are some examples of vectors
A
- velocity
- displacement
- acceleration
- force
- momentum
5
Q
how do we represent vectors
A
use arrows
length = the magnitude
the way it is pointing = the direction
6
Q
define the term force and what are they measured in
A
a push or pull that acts on an object due to its interaction with another
newtons (N)
7
Q
what are contact forces and non contact forces
A
where the two objects physically touch
where the two objects don’t need to be physically touching
8
Q
what are some examples of contact forces
A
friction, air resistence, tension
9
Q
what are reaction forces (or normal contact forces)
A
when two objects propose equal and opposite force
10
Q
what are some examples of non contact forces
A
gravitational, magnetic, electrostatic
11
Q
what happens to the strength of a non contact force as they get further apart
A
decrease
12
Q
what do free body diagrams show
A
all the forces that are acting on an object
13
Q
define resultant force
A
the overall force on an object
14
Q
what does equilibrium mean
A
when all the forces acting on an object are balanced
15
Q
define gravity
A
a force of attraction between two objects dependent on the mass of the object and how far apart the two objects are
16
Q
what is gravitation feild strength
A
the gravitational force in newtons that acts on a mass of one kilogram.
17
Q
what is the gravitation feild strength of the earth and the moon
A
earth - 9.8 N/kg
moon - 1.6 N/kg
18
Q
what is the difference between weight and mass
A
weight - a measure of the size of the pull of gravity on the object
mass - a measure of how much matter there is in an object
19
Q
what is gravitation potential energy and what is it measured in
A
the energy an object has by virtue of its position above the surface of the Earth
joules (J)
20
Q
define work done
A
a measure of energy transfer used when a force is used to move an object by a certain distance
work done is the energy that is required
21
Q
what is power and work done measured in
A
power - Watts (W)
work done - Joules (J)
22
Q
how do you go from J to kJ
how do you go from g to Kg
A
divide by 1000
23
Q
what is elasticity
A
the ability of an object or material to resume its normal shape after being stretched or compressed
24
Q
what is it called when an object is changed shape and what are the two types
A
it is being deformed
elastic and inelastic
25
what is the difference between elastic and inelastic deformation
elastic deformation occurs when an object turns back to its original shape after force is applied and removed
inelastic deformation occurs when an object doesn't turn back into its original shape
26
define extension
the increase of length of a spring when it is stretched
27
what is the relationship between the force applied to an object and the extension of an elastic object
the extension is directly proportional to the force applied
28
what type of energy is stored in a spring when it is stretched
elastic potential
29
what are the two equations for elasticity
f=k e
ek= 1/2 k e^2
30
what is the alternate name for the turning effect of a force
a moment
31
define a moment
the rotational or turning effect of a force
32
what is the equation for a moment
moment = force x distance
33
when finding out a moment what does the distance measure
how far away the force is to the pivot
34
if an object is at equilibrium what can be said about the moments acting on an object
the clockwise moments are equal to the anticlockwise moments
35
what are levers and give two examples
transmit the turning effect of a force
- scissors
- wheelbarrow
36
what will happen if the input and output forces are on different sides of the pivot
the forces will act in different directions
37
what three parts make up a lever system
load
effort
pivot
38
when calculating a moment what must you convert
cm into m for the distance
39
what are gears
they transmit turning effects
40
what is meant by the term fluid
a liquid or gas
41
define pressure
force per the unit of area
42
what is the equation for pressure
P = F / A
43
how is pressure created in a container of gas
the partials constantly collide into surroundings and generate pressure as each collision applies a force to the inside area of the container
44
what is the perpendicular force and hoe does this effect pressure
component of the force at which it is at right angles to the surface it is colliding with
- particles that create a higher perpendicular force generate more pressure
45
what determines the pressure on an object when in water
- the surrounding water molecules surrounding with the object
- the downwards force of the weight of water above the object
- the density of the liquid
- the gravitational feild strength
46
what is the equation for pressure in a liquid
pressure = height of liquid above the object x density of liquid x gravitational feild strength
47
what is pressure measured in
Pa (pascals)
48
define upthrust
the resultant upward force
49
what two components effect weather an object sinks or floats
the upthrust acting on the object, the objects weight, the density of fluid
50
what is the worlds atmosphere
a thin layer of gasses that surround the entire planet made mostly of nitrogen and some oxygen. as well as greenhouse gasses
51
what happens to the density of the atmosphere with increasing altitude
the atmosphere becomes less dense as altitude increases
52
explain why atmospheric pressure decreases with increasing altitude
- pressure is created by the collisions of air molecules
- the quantity of molecules decreases with increasing altitude
- therefore less collisions occur
53
what quantity is speed and what quantity is velocity
scalar
vector
54
what quantity is distance and what quantity is displacement
scalar
vector
55
define displacement
the action of moving something from its place or position.
56
what is the equation for displacement
the same as speed - distance/ time
but its just
displacement / time
57
what is the typical speed of sound
330 m/s
58
what is the typical speed of human walking, running and cycling
1.5 m/s
3 m/s
6 m/s
59
why can an object travelling at a constant speed in a circle not have constant velocity
speed is a scalar quantity
velocity is a vector quantity meaning it can only be constant if the direction is constant
in a circular motion, the direction is constantly changing
60
how can speed be calculated from a distance time graph
the speed is equal to the gradient of the line
61
what must be done to calculate speed at a given time from a distance time graph
draw a tangent to the curve at a required time and find the gradient of the tangent
62
how can the distance travelled by an object be calculated from a velocity time graph
equal to the area under the graph
63
on a velocity time graph what tells you the acceleration
the gradient
change in velocity/change in time
64
define acceleration
the rate of change in velocity
- how quickly something speeds up or slows down
65
what are the equations for acceleration
acceleration = change in velocity/ time
or
acceleration = v-u/time
final velocity - initial velocity
66
what is the another equation for acceleration that uses distance
2 a s = v^2 - u^2
s=distance
67
what is terminal velocity
when an objects velocity remains constant and they are no longer accelerating or decelerating
68
give a value for the acceleration of an object in free fall under gravity near earths surface
9.8m/s^2
69
what can be said about the resultant force acting on an object when it is falling at terminal velocity
there will be 0 resultant force and will now be moving at a constant force
70
what is the relationship between an objects air resistance and weight when it starts falling
therefore where is the resultant force
and what does this lead to
their weight would be much larger than the air resistance or drag
- in a downwards direction
- acceleration toward the ground
71
when an object is falling what happens to the acceleration of the object in order to reach terminal velocity
acceleration increases until the weight and drag is equal where is then reaches its terminal velocity
72
what is Newtons first law of motion
a resultant force is required to change the motion of an object
- unless acted upon a resultant force an object at rest will remain at rest and an object in motion will remain in motion
73
what is Newtons second law of motion
if a non zero resultant force acts on an object it will cause the object to accelerate
74
what does Newtons second law of motion dependent on
the initial motion of the partial
75
what are the five initial motions of partials and how does adding a non zero resultant force affect that
1. stationary - the object will start moving
2. moving to the right - the object will speed up
3. travelling to the left- the object will slow down
4. travelling slowly - the object will stop
5. a change in direction may occur
76
what is the second part of Newtons second law
the size of the resultant force is directly proportional to the acceleration it causes
77
state the equation for Newtons second law
F = ma
resultant force = mass x acceleration
78
define inertia
the tendency for the motion of an object to remain unchanged
- a measure of how difficult it is to change an objects given velocity
79
what is the equation for inertial mass and what is it the same as
force/acceleration
newtons second law
80
what is Newtons third law
when two objects interact the forces they exert on each other are equal and opposite
81
define stopping distance
the minimum distance required to stop a vehicle in an emergency
82
what is the equation for stopping distance
stopping distance =
thinking distance+ breaking distance
83
what is the thinking distance
how far the car travels during the drivers reaction time
84
what is the reaction time
the time between a driver seeing a hazard and applying the breaks
85
what are the two mains things that determine the thinking distance
the speed - faster your going the further you will travel
reaction time - vary between people
86
how can peoples reaction time be increased
tired, drunk, in drugs, distracted
87
what is the breaking distance
the distance taken to stop under the breaking force
88
what are the factors that effect breaking distance and why
1. speed
- mass
they both increase vehicles kinetic energy
2. condition and quality of breaks
wont slow car down quickly and therefore will take longer to slow
3. traction between car and road
- icy or wet - les friction
- tires have no tread left - cant grip road
89
what is the equation and the quality of momentum
mass x velocity
vector
90
what is the conservation of momentum principle
the idea that in a closed system the total momentum before an event ( like a collision) is the same as the total momentum after an event
91
what is the letter symbol for momentum
p
92
what is the equation linking change in momentum, force and time
change in momentum = force x time
93
explain how wearing a seatbelt improves a passengers safety during collisions
1. stop you flying out of car
2. slightly stretchy and therefore slow you down more slowly
increase the time taken for momentum to be lost meaning a lower force is acted on a person
94
explain how crumple zones improves a passengers safety during collisions
there is a small amount of extra time for the car to loose momentum as it crumples
increase time taken for momentum to be lost meaning a lower force is acted on a person
