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Physics > Forces and Motion > Flashcards

Forces and Motion Flashcards

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1
Q

Nano (metre)

A

x 10 *-9

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2
Q

Micro (metre)

A

x 10 *-6

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3
Q

Milli (metre)

A

x 10 *-3

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4
Q

Hecto (pascal)

A

x 10 *2

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5
Q

kilo (pascal)

A

x 10 *3

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6
Q

mega (metre)

A

x 10 *6

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7
Q

Giga (metre)

A

x 10 *9

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8
Q

In equations, charge is represented by … and measured in …

A

Q
Coulombs (C)

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9
Q

Acetate always

A

Gives away electrons and
is always positive
ACETATE IS GREAT

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10
Q

Polythene always

A

Takes electrons and
is always negative
POLYTHENE IS MEAN

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11
Q

What happens if you rub a neutrally charged balloon onto a neutrally charged jumper

A
  • causes friction which causes electrons to move
  • leaving one negatively charged and the other positively charged
  • so they will stick
  • because opposites attract
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12
Q

What happens if you hold a negatively charged balloon next to a neutrally charged wall

A
  • it would stick
  • because the electrons in the balloon and the wall will repel
  • inducing a positive charge in the wall
  • and opposites attract
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13
Q

Describe how a dust print lifter works

A
  • lifting sheet is placed over footprint
  • metal plate is placed near it
  • a control unit connecting both applies a voltage between them
  • lifting sheet = negative, metal plate = positive
  • The electrons in the dust repel away from their like charges leaving the protons to attract to the paper
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14
Q

Describe how a photocopier works

A
  • an area of a cylindrical drum is given a positive charge
  • light is projected and an image is formed on this area so that the charge only stays on the shape that is to be printed
  • toner (negatively charged) is dropped onto the drum, sticks to charged areas
  • excess toner is removed
  • paper is pressed against drum
  • paper is heated to melt toner which forms the permanent image on the paper
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15
Q

How to prevent sparks/explosions when refuelling aircraft

A

Earth the plane using a conductor allowing the charge that built up to flow to earth.

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16
Q

Uses of electrostatics

A

Paint spraying, photocopier, crop spraying(insecticide is sprayed)

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17
Q

Dangers of electrostatics

A

Lightning, refuelling aircraft,

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18
Q

Describe how lightning works

A

A build up of positive charge accumulates on the ground beneath the cloud attracted to the negative charge in the bottom of the cloud. If the difference in the charges is enough, lightning will strike that place

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19
Q

Symbol for current in an equation is … and is measured in …

A

I Capital i
Amperes (Amps) A

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20
Q

what is Current

A

the rate of flow of charge

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21
Q

State the equation linking current time and charge & then the symbols then the units

A

Charge = current x time
Q = It
Coulombs = Coulombs/second x seconds

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22
Q

What is the difference between a distance-time graph and a displacement-time graph

A

Displacement graphs are able to show direction aswell whereas distance graphs tend not to

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23
Q

what is velocity

A

Speed with a direction

Eg. v = -10m/s v = 10m/s
SPEED for both is 10m/s
VELOCITY adds + or - depending on direction

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24
Q

What does the gradient on a distance-time graph show

A

Velocity

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25
Q

Equation to find ACCELERATION and then symbols

A

acceleration = final velocity-initial velocity / time

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26
Q

What is acceleration

A

the rate of change of velocity

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27
Q

State the equation linking time distance and velocity

A

Distance = velocity x time

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28
Q

How do you work out the distance travelled on a velocity-time graph

A

Find the area under the line

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29
Q

Basic facts about Ticker Timers

A

Time taken between each dot is always the same
The distance varies depending on speed

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30
Q

What is a vector quantity

A

A vector quantity has both direction and magnitude

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31
Q

What is a scalar quantity

A

A scalar quantity has only magnitude

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32
Q

Give some examples of vectors

A

Acceleration
Current
Displacement
Moment
etc

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33
Q

Give some examples of scalars

A

Charge
volume
Time Temperature
etc

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34
Q

What is displacement

A

How far you move in a given direction

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35
Q

State the equation linking mass acceleration and force and symbols then units

A

Force = mass x acceleration
F = MA
N = kg x m/s*2

36
Q

Describe Newton’s 3 laws

A
  • if there are no forces acting on an object which is not moving, it will stay at rest. If it was already moving at a steady state in a straight line then it will continue to move as before
  • If a force is applied to an object then it will change its speed in the same direction as the force
  • For each force there is another force acting in the opposite direction with the same strength
37
Q

Give four methods to investigate motion

A

light gate
ticker tape
motion sensors
stopwatch and tape measure

38
Q

What is weight and what is it measured in

A

The force of attraction an object feels towards another object. Newtons (N)

39
Q

What is Mass and what is it measured in

A

The number and type of atoms in an object. (Kg)

40
Q

State the equation linking Gravitational field strength, mass and weight and the symbols

A

Weight = mass x gravitational filed strength
W = mg

41
Q

What equation is the same as W = mg

A

F = ma

42
Q

What equation is the same as F = ma

A

W = mg

43
Q

State the equation linking Braking distance, Thinking distance and stopping distance

A

Stopping Distance = Thinking distance + Braking distance

44
Q

Thinking distance is affected by

A

Alcohol
Tiredness

45
Q

Braking Distance is affected by

A

Worn down tires/brakes
Slippery surface (weather)
Angle of surface (Hill)

46
Q

Explain terminal velocity

A
  • At the start = only one force = weight so accelerate
  • A slip second later, air resistance will be acting the other way but as the forces are unequal, acceleration
  • As acceleration increases, air resistance increases
  • Air resistance keeps increasing until it becomes equal to the weight of the object and
  • so the resultant force is 0
  • so he will reach his terminal velocity and travel at a constant speed
47
Q

how to find acceleration on a velocity-time graph

A

gradient

48
Q

what would to an object with balanced forces acting on it

A

it will stay at rest or stay in constant motion as its resultant force is 0

49
Q

what would happen to an object if an unbalanced force was acting on it

A
  • the direction of the object’s acceleration is the same as the direction of the unbalanced force
  • the magnitude of the object’s acceleration varies in direct proportion with the size of the unbalanced force
50
Q

four ways to investigate motion

A
  • motion sensors (reflected sound)
  • ticker tape
  • light gate
  • stopwatch and tape measure
51
Q

what is mass

A

the number and type of atoms in an object (kg)

52
Q

what is weight

A

the force of attraction an object feels towards another object (typically a planet/star) (n)

53
Q

difference between normal reaction force and upthrust

A

normal reaction force happens ALL the time whereas upthrust only happens in fluids

54
Q

practical to find speed

A

use a ticker tape timer attached to a trolley pulled across a bench/down a ramp
(normally 50 dots per second)

55
Q

is force a scalar or a vector quantity

A

vector

56
Q

friction is a force that opposes ……..

A

motion

57
Q

equation to find force

A

f = ma

58
Q

equation to find wieght

A

W = mg

59
Q

equation to find stopping distance

A

stopping distance = thinking distance + braking distance

60
Q

factors that affect a vehicle’s stopping distance

A
  • speed
  • mass (momentum)
  • road condition
  • weather
  • brake pad age and wear
  • inebriation
  • reaction time
61
Q

describe how terminal velocity is reached

A

Immediately on leaving the aircraft, the skydiver accelerates downwards due to the force of gravity and his weight. There is no air resistance acting in the upwards direction, and there is a resultant force acting downwards so the skydiver accelerates towards the ground.
As the skydiver gains speed, their weight stays the same but the air resistance increases. There is still a resultant force acting downwards, but this gradually decreases.
Eventually, the skydiver’s weight is balanced by the air resistance/friction. There is no resultant force so there is no more acceleration and the skydiver reaches terminal velocity.

62
Q

state the equation linking force, sprint constant and extension

A

force = spring constant x extension

63
Q

what is Hooke’s Law

A

within the elastic region, extension is proportional to the force applied

64
Q

what is elastic behaviour

A

when a material returns to an original size and shape when you remove the forces deforming it

65
Q

what is plastic behaviour

A

a plastic material is one that stays deformed after you take the force away

66
Q

how can you explain the initial linear region of a force-extension graph

A

using Hooke’s Law

67
Q

what is Newton’s third law

A

whenever two objects interact, they exert equal and opposite forces on each other.
(a skateboarder pushing another and they both move at the same acceleration away if they are at the same mass because f=ma. if one skateboarder is double the mass of the other he will move away half as far)

68
Q

equation for moment

A

moment = force x perpendicular distance form pivot

69
Q

where does the weight of a body act

A

through its centre of gravity

70
Q

the upward forces on a light bean, supported at its ends, vary with ……

A

the position of a heavy object placed on the beam

71
Q

what is spring constant

A

measures how stiff the spring is

72
Q

in what ways can forces affects other objects

A
  • speed them up or down
  • change their shape
  • change their direction
73
Q

newtons first law

A

an object remains in the same state of motion unless a resultant force acts on it.

74
Q

newtons second law

A

f = ma

75
Q

how to find a 2D shape’s centre of gravity

A

Put a pin attached to a freely hanging string into the freely hanging shape and draw a line where the string hangs
- put the pin in other random places along the edge of the shape and where they meet is the centre of gravity

76
Q

How to measure the speed of an object using light gates

A

the vehicle must have a card attached to the top (an interrupter) in order to break the beam.
- then lets say the interrupter take 0.02s to pass through the gate, if the interrupter is 10cm then the speed (=distance/time) is 5m/s

77
Q

what does the gradient tell you on a velocity-time graph

A

acceleration

78
Q

what does the area under a velocity-time graph tell you

A

distance travelled

79
Q

what is the relationship between: final speed, initial speed, acceleration, and distance moved

A

v^2 = u^2 + (2 x a x s)

80
Q

experiment to investigate the motion of a toy car on a ramp

A
81
Q

How long is the bus stationary

A

10 secs

82
Q

What is Hookes law

A

extension is proportional to the amount of force applied up to the limit of proportionality

83
Q

when a skater throws a snowball, she slides backwards on the ice. explain why she moves in that direction

A
  • newton’s third law - every action has an equal and opposite reaction
  • so forces are acting on both the snowball and the skater
  • and they are equal and opposite
  • so the rate of change of momentum is the same for both forces
84
Q

in what three ways can forces affect bodies

A
  • speed - speed up or slow down
  • direction - change direction of travel
  • shape - stretch, compress, or deform
85
Q

what region of a force-extension graph is associated with Hooke’s law

A

the initial linear region

86
Q

how do you calculate the momentum of a car after a crash

A

conservation of momentum

87
Q

what is Newton’s third law

A

Whenever two bodies interact, the forces they exert on each other are equal and opposite

Physics (13 decks)

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