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Physics-Zoe Brown > Topic 1,2&3 > Flashcards

Topic 1,2&3 Flashcards

1
Q

Vector quantities

A

Have magnitude and a direction

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2
Q

Examples of vector quantities

A

Force,velocity,displacement,weight,acceleration,momentum

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3
Q

Scalar quantities

A

Only have magnitude and no direction

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4
Q

Examples of scalar quantities

A

Speed,distance,mass,energy,

temperature, time

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5
Q

Displacement

A

Measures the distance and direction in a straight line from an objects starting point to its finishing point

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6
Q

How to calculate speed,distance and time

A

Distance travelled
—————————
Speed X Time

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7
Q

Velocity

A

Is speed in a given direction

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8
Q

How to work acceleration

A

A = (v-u)
——
T

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9
Q

Uniform acceleration (constant acceleration)

A

V^2-u^2 = 2 X a X x

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10
Q

Distance/Time graphs

A
  • the gradient at any point gives the speed of the object
  • flat sections are where it’s stopped
  • a steeper graph means it’s going faster
  • curves represent acceleration
  • a curve getting steeper means it’s speeding up
  • a levelling off curve means it’s slowing down
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11
Q

If distance/time graph is a straight line what is the speed

A

Speed = gradient =
change in the vertical
——————————
Change in the horizontal

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12
Q

Velocity/Time graphs

A
  • gradient=acceleration
  • flat sections represent a steady speed
  • the steeper the graph the greater the acceleration or deceleration
  • uphill sections are acceleration
  • downhill sections are deceleration
  • a curve means changing acceleration
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13
Q

How to find the distance travelled in a certain Time on a velocity/time graph

A

The area under any section of the graph is equal to the distance travelled in that time interval

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14
Q

What s Newton’s first law

A

That a resultant force is needed to make something start moving,speed up or slow down

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15
Q

Newton’s second law formula

A 
F= m x a
Or 
F= change in momentum
     ——————————–
                   Time
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16
Q

Weight

A

The force acting on an object due to gravity

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17
Q

How is mass and weight measured

A

Mass is measured kg with a mass balance whereas weight is measured in newtons using a calibrated spring balance

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18
Q

How to calculate weight

A

Weight
——————————
Mass x gravitational field strength

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19
Q

Centripetal force

A

The force acting towards the centre of the circle that keeps something moving in a circle

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20
Q

Trolley on ramp-investigating motion

A
  1. measure mass of trolley,unit masses and hanging hook.measure length of card on the trolley which will interrupt the light gate beams
  2. adjust height of ramp until trolley just starts to move
  3. mark line on ramp just before 1st light gate to make sure trolley travels same distance every time
  4. attach trolley to hanging masses by string then hold trolley still then let go timing with a stop watch the time taken for the trolley to travel from one light gate to next or using light gates that time for you
  5. the light gates will record the speed of the trolley
  6. Then you can work out acceleration
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21
Q

What would you use to find a persons walking speed

A

A rolling tape measure and markers to measure and mark our distances. And for any times longer than 5 seconds a stopwatch can be used

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22
Q

What’s inertia

A

The tendency for motion to remain unchanged and keep moving with the same velocity

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23
Q

Inertial mass

A

Measured how difficult it is to change the velocity of an object define as ratio of force over acceleration

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24
Q

Newtons 3rd law

A

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

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25
Q

Momentum

A

The product of the objects mass and velocity

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26
Q

How to calculate momentum

A

P = m x v

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27
Q

Conservation of momentum

A

The total momentum before an event is the same as after the event

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28
Q

Closed system

A

No external forces act

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29
Q

Forces causing changes in momentum

A

-a resultant force on an object causes it to accelerate

30
Q

What’s thinking distance

A

The distance the car travels in the drivers reaction time (the time between noticing hazard and applying brakes)

31
Q

2 things thinking distance is affected by

A
  1. Reaction time-this is increased by tiredness,alcohol,drugs and distractions
  2. speed-the faster you’re going the further you’ll travel during reaction time
32
Q

What’s Braking distance

A

The distance taken to stop once the brakes have been applied

33
Q

Why is stopping distance affected by

A
  1. speed-faster you’re going longer it takes to stop
  2. mass of car-a heavier car will take longer to stop
  3. condition of brakes-worn/faulty brakes won’t be able to brake with as much force
  4. how much friction is between tyres and road- more likely to skid if road is dirty wet or icy
34
Q

Stopping distance

A

The distance it takes to stop a car. Thinking distance + braking distance

35
Q

Ruler drop experiment to measure reaction time

A
  • get some one else to hold a ruler so it hangs between your thumb and forefinger,lined up with 0
  • without warning person holding ruler drops it
  • close your thumb and finger to catch it as quickly as possible
  • the measurement on the ruler at the point where it was caught is how far the ruler dropped in the time it took to react
  • longer distance lover reaction time
36
Q

Energy in the cars kinetic energy store = work done by the brakes

A

1/2 x m x v^2 = F x d

37
Q

What are the approximate masses of a car, a loaded lorry and a single decker bus

A

Car ~ 1000kg
Loaded lorry ~ 30,000kg
Single decker bus ~ 10,000kg

38
Q

Energy transferred between energy stores

A 
Kinetic
Thermal
Chemical
Gravitational potential
Elastic potential
Electrostatic
Magnetic
Nuclear
39
Q

Calculate kinetic energy

A

KE = 1/2 x m x v^2

40
Q

Calculate change in gravitational potential energy

A

Change in GPE = m x g x change in h

41
Q

What are the 4 ways energy can be transferred between stores

A
  1. mechanically- a force acting on an object
  2. electrically- a charge doing work against resistance
  3. by heating- energy transferred from a hotter object to a colder object
  4. by radiation- energy transferred by waves
42
Q

How to calculate efficiency

A

Efficiency=
useful energy transferred by device
—————————————————
Total energy supplied to device

43
Q

What does the conservation of energy principle mean

A

Total energy input= useful energy output + wasted energy

44
Q

What can be used to reduce unwanted energy transfer

A
  • reduce friction for objects touching each other lubricants they reduce energy transferred by friction
  • thermal insulation prevent heat loss
45
Q

Conduction

A

When an object is heated the particles vibrate more and collide with each other

46
Q

Disadvantages of non-renewable resources

A
  • burning coal and oil realises sulphur dioxide which causes acid rain
  • nuclear waste is very dangerous
  • fossil fuels release co2 when burned which adds to greenhouse effect
47
Q

Advantages of non-renewable energy resources

A
  • cheap to extract fossil fuels
  • fossil fuel power plants are cheap to build
  • not running out yet
48
Q

Advantages of renewable energy resources

A
  • never run out

- less damage to environment that non-renewables

49
Q

Disadvantages of renewable energy resource

A
  • don’t provide much energy

- some are unreliable because depend on weather

50
Q

Examples of renewable energy resource

A 
Bio-fuels
Wind
The sun (solar)
Hydro-electricity
Tides
51
Q

Bio-fuels

A

Created from either plant products or animal dung

  • cost to refine them is very high
  • Large areas of forest cleared to make room to grow bio-fuels results in loss of habitats
  • decay/burning of this cleared vegetation increases methane and co2 emissions
52
Q

Wind power

A

Wind rotates blades which turn generator and produce electricity

  • initial costs are high but running costs are minimal
  • lots of wind turbines are needed to produce enough power
  • spoil view
  • only work when windy
  • no pollution
53
Q

Solar power

A

Solar cells are made from materials that use energy transferred by light to create an electric current

  • no pollution
  • initial costs are high but basically no running costs
  • no solar power produced at night
54
Q

Hydro-electricity

A

Involves flooding a valley by building a big dam.rainwater is caught and allowed out through turbines

  • no pollution
  • loss of habitats
  • can immediately respond to increased electricity demand
  • initial costs are high,running costs minimal
55
Q

Tides/tidal barrages

A

Big dams built across river estuaries with turbines in them,as tide comes in it fills up estuary.water is let out through turbines at a controlled speed to generate electricity

  • no pollution
  • affect boat access
  • reliable
  • initial costs are moderately high but no fuel costs and minimum running costs
  • barrages don’t work when water level is same either side
56
Q

Insulation- thermal conductivity

A

Thermal conductivity describes how well a material transferred energy by conduction. In buildings, lower the thermal conductivity of walls, slower rate of energy transfer through them

57
Q

Typical speeds for transport methods

A 
Walking- 1.4m/s
Running- 3m/s
Cycling- 5.5m/s
Aeroplanes- 250m/s 
Trains- 31m/s
Wind- 5-20m/s
Sound in air- 340m/s
Ferries- 15m/s 
Cars- 13-31m/s
58
Q

what is acceleration in free fall

A

10m/s^2

59
Q

what happens where resultant force on body is zero

A

the body is moving at constant velocity or is at rest

60
Q

what happens where the resultant force on a body is not zero

A

speed and/or direction changes

61
Q

what does it mean when an object is moving in a circular orbit at a constant speed

A

it is constantly changing direction, so constantly changing velocity

62
Q

describe an example of momentum in a collision

A

red ball stationary so has 0 momentum, white ball moving with velocity v, so has momentum p=mxv. white ball hits red ball causing it to move. red ball now has momentum. white ball continues to move but at smaler velocity. combine momentum of red and white balls is equal to original momentum of white ball

63
Q

explain dangers caused by large deceleration and estimate forces involved in typical situations on public road

A

as speed increases, thinking distance increases at same rate. because drivers reaction time stays fairly constant but higher speed further you go in that time. braking distance and speed have a squared relationship

64
Q

analyse changes involved in way energy is stored when a ball is rolling up a slope

A

ball does work against gravitational force, so energy transferred mechanically form KE store of ball to its GPE store

65
Q

analyse changes involved in way energy is stored when a bat hits a ball

A

bat has energy in its KE store. some of this transferred mechanically to ball’s KE store. some energy transferred mechanically to thermal energy stores of bat and ball. rest carried away by sound

66
Q

analyse changes involved in way energy is stored when a rock is dropped from a cliff

A

assuming no air resistance, gravity does work on rock so rock constantly accelerates towards ground. Energy transferred mechanically from rock’s GPE store to its KE store

67
Q

analyse changes involved in way energy is stored when a car slows down

A

energy in KE store of car transferred mechanically, and then by heating, to thermal energy stores of car and road

68
Q

analyse changes involved in way energy is stored when a kettle boils water

A

energy transferred electrically from mains to heating element of kettle, and then by heating to thermal energy stores of water

69
Q

where there are energy transfers in closed system what happens to total energy

A

no net change in total energy in closed system

70
Q

what does it mean when mechanical processes cause a rise in temperature

A

they become wasteful because dissipating energy in heating the surroundings

71
Q

in energy transfers what always happens

A

some of input energy is always dissipated or wasted, often to thermal energy stores. eg. whenever work done mechanically frictional forces have to be overcome, energy needed to do this transferred to thermal energy stores of whatever doing work and surroundings

Physics-Zoe Brown (14 decks)

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