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forces Flashcards

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1
Q

what are scalers

A

physical quantities that only have a magnitude (size)

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2
Q

what are some examples of scalars

A
  • speed
  • distance
  • mass
  • temperature
  • time
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3
Q

what are vectors

A

quantities with both magnitude and direction

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4
Q

what are some examples of vectors

A
  • velocity
  • displacement
  • acceleration
  • force
  • momentum
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5
Q

how do we represent vectors

A

use arrows
length = the magnitude
the way it is pointing = the direction

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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)

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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

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8
Q

what are some examples of contact forces

A

friction, air resistence, tension

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9
Q

what are reaction forces (or normal contact forces)

A

when two objects propose equal and opposite force

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10
Q

what are some examples of non contact forces

A

gravitational, magnetic, electrostatic

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11
Q

what happens to the strength of a non contact force as they get further apart

A

decrease

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12
Q

what do free body diagrams show

A

all the forces that are acting on an object

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13
Q

define resultant force

A

the overall force on an object

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14
Q

what does equilibrium mean

A

when all the forces acting on an object are balanced

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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

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16
Q

what is gravitation feild strength

A

the gravitational force in newtons that acts on a mass of one kilogram.

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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

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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

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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)

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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

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21
Q

what is power and work done measured in

A

power - Watts (W)
work done - Joules (J)

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22
Q

how do you go from J to kJ
how do you go from g to Kg

A

divide by 1000

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23
Q

what is elasticity

A

the ability of an object or material to resume its normal shape after being stretched or compressed

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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

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25
Q

what is the difference between elastic and inelastic deformation

A

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

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26
Q

define extension

A

the increase of length of a spring when it is stretched

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27
Q

what is the relationship between the force applied to an object and the extension of an elastic object

A

the extension is directly proportional to the force applied

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28
Q

what type of energy is stored in a spring when it is stretched

A

elastic potential

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29
Q

what are the two equations for elasticity

A

f=k e
ek= 1/2 k e^2

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30
Q

what is the alternate name for the turning effect of a force

A

a moment

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31
Q

define a moment

A

the rotational or turning effect of a force

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32
Q

what is the equation for a moment

A

moment = force x distance

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33
Q

when finding out a moment what does the distance measure

A

how far away the force is to the pivot

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34
Q

if an object is at equilibrium what can be said about the moments acting on an object

A

the clockwise moments are equal to the anticlockwise moments

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35
Q

what are levers and give two examples

A

transmit the turning effect of a force
- scissors
- wheelbarrow

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36
Q

what will happen if the input and output forces are on different sides of the pivot

A

the forces will act in different directions

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37
Q

what three parts make up a lever system

A

load
effort
pivot

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38
Q

when calculating a moment what must you convert

A

cm into m for the distance

39
Q

what are gears

A

they transmit turning effects

40
Q

what is meant by the term fluid

A

a liquid or gas

41
Q

define pressure

A

force per the unit of area

42
Q

what is the equation for pressure

A

P = F / A

43
Q

how is pressure created in a container of gas

A

the partials constantly collide into surroundings and generate pressure as each collision applies a force to the inside area of the container

44
Q

what is the perpendicular force and hoe does this effect pressure

A

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
Q

what determines the pressure on an object when in water

A
  • 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
Q

what is the equation for pressure in a liquid

A

pressure = height of liquid above the object x density of liquid x gravitational feild strength

47
Q

what is pressure measured in

A

Pa (pascals)

48
Q

define upthrust

A

the resultant upward force

49
Q

what two components effect weather an object sinks or floats

A

the upthrust acting on the object, the objects weight, the density of fluid

50
Q

what is the worlds atmosphere

A

a thin layer of gasses that surround the entire planet made mostly of nitrogen and some oxygen. as well as greenhouse gasses

51
Q

what happens to the density of the atmosphere with increasing altitude

A

the atmosphere becomes less dense as altitude increases

52
Q

explain why atmospheric pressure decreases with increasing altitude

A
  • pressure is created by the collisions of air molecules
  • the quantity of molecules decreases with increasing altitude
  • therefore less collisions occur
53
Q

what quantity is speed and what quantity is velocity

A

scalar
vector

54
Q

what quantity is distance and what quantity is displacement

A

scalar
vector

55
Q

define displacement

A

the action of moving something from its place or position.

56
Q

what is the equation for displacement

A

the same as speed - distance/ time
but its just
displacement / time

57
Q

what is the typical speed of sound

A

330 m/s

58
Q

what is the typical speed of human walking, running and cycling

A

1.5 m/s
3 m/s
6 m/s

59
Q

why can an object travelling at a constant speed in a circle not have constant velocity

A

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
Q

how can speed be calculated from a distance time graph

A

the speed is equal to the gradient of the line

61
Q

what must be done to calculate speed at a given time from a distance time graph

A

draw a tangent to the curve at a required time and find the gradient of the tangent

62
Q

how can the distance travelled by an object be calculated from a velocity time graph

A

equal to the area under the graph

63
Q

on a velocity time graph what tells you the acceleration

A

the gradient
change in velocity/change in time

64
Q

define acceleration

A

the rate of change in velocity
- how quickly something speeds up or slows down

65
Q

what are the equations for acceleration

A

acceleration = change in velocity/ time

or

acceleration = v-u/time
final velocity - initial velocity

66
Q

what is the another equation for acceleration that uses distance

A

2 a s = v^2 - u^2

s=distance

67
Q

what is terminal velocity

A

when an objects velocity remains constant and they are no longer accelerating or decelerating

68
Q

give a value for the acceleration of an object in free fall under gravity near earths surface

A

9.8m/s^2

69
Q

what can be said about the resultant force acting on an object when it is falling at terminal velocity

A

there will be 0 resultant force and will now be moving at a constant force

70
Q

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

A

their weight would be much larger than the air resistance or drag

  • in a downwards direction
  • acceleration toward the ground
71
Q

when an object is falling what happens to the acceleration of the object in order to reach terminal velocity

A

acceleration increases until the weight and drag is equal where is then reaches its terminal velocity

72
Q

what is Newtons first law of motion

A

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
Q

what is Newtons second law of motion

A

if a non zero resultant force acts on an object it will cause the object to accelerate

74
Q

what does Newtons second law of motion dependent on

A

the initial motion of the partial

75
Q

what are the five initial motions of partials and how does adding a non zero resultant force affect that

A
  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
Q

what is the second part of Newtons second law

A

the size of the resultant force is directly proportional to the acceleration it causes

77
Q

state the equation for Newtons second law

A

F = ma
resultant force = mass x acceleration

78
Q

define inertia

A

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
Q

what is the equation for inertial mass and what is it the same as

A

force/acceleration
newtons second law

80
Q

what is Newtons third law

A

when two objects interact the forces they exert on each other are equal and opposite

81
Q

define stopping distance

A

the minimum distance required to stop a vehicle in an emergency

82
Q

what is the equation for stopping distance

A

stopping distance =
thinking distance+ breaking distance

83
Q

what is the thinking distance

A

how far the car travels during the drivers reaction time

84
Q

what is the reaction time

A

the time between a driver seeing a hazard and applying the breaks

85
Q

what are the two mains things that determine the thinking distance

A

the speed - faster your going the further you will travel
reaction time - vary between people

86
Q

how can peoples reaction time be increased

A

tired, drunk, in drugs, distracted

87
Q

what is the breaking distance

A

the distance taken to stop under the breaking force

88
Q

what are the factors that effect breaking distance and why

A
  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
Q

what is the equation and the quality of momentum

A

mass x velocity
vector

90
Q

what is the conservation of momentum principle

A

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
Q

what is the letter symbol for momentum

A

p

92
Q

what is the equation linking change in momentum, force and time

A

change in momentum = force x time

93
Q

explain how wearing a seatbelt improves a passengers safety during collisions

A
  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
Q

explain how crumple zones improves a passengers safety during collisions

A

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

physics two (4 decks)

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