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physics > motion, forces and conservation of energy > Flashcards

motion, forces and conservation of energy Flashcards

1
Q

what do vectors have

A

magnitude and direction

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2
Q

what do scalars have

A

just magnitude

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3
Q

examples of vector quantities

A

force, velocity, displacement, weight, acceleration, momentum

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4
Q

examples of scalar quantities

A

speed, distance, mass, energy, temperature, time

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5
Q

what is distance

A

how far the object moved

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6
Q

what is displacement

A

the distance and direction in a straight line from the starting point

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7
Q

what is speed

A

how fast your going

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8
Q

what is velocity

A

speed in a given direction

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9
Q

walking speed

A

1.4m/s

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10
Q

what is running speed

A

3m/s

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11
Q

what is the speed of a aeroplane

A

250m/s

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12
Q

equation for distance travelled (m)

A

average speed (m/s) x time (s)

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13
Q

equation of acceleration

A

v-u (change in velocity: v is final, u is initial) / t

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14
Q

what is acceleration

A

change in velocity in a certain amount of time

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15
Q

what is deceleration

A

negative acceleration

if something slows down - change in velocity is negative

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16
Q

how to estimate acceleration

A
  1. estimate how long it would take the car to stop
  2. put these numbers into the accelerating equ
  3. as the car slowed down, change in velocity and acceleration is negative - car is decelerating
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17
Q

another word for constant acceleration

A

uniform acceleration

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18
Q

equ for uniform acceleration

A

v (squared) - u (squared) = 2 x a x X (distance)

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19
Q

what do distance time graphs show (2)

A

how far something has travelled and the speed of the object

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20
Q

what does the gradient on a distance time graph show

A

speed of the object

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21
Q

what does the flat section on a distance time graph show

A

where it’s stopped

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22
Q

what does the steeper graph on a distance time graph show

A

going faster

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23
Q

what does the curves on a distance time graph show

A

acceleration

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24
Q

what does the curve getting steeper on a distance time graph show

A

speeding up (increasing gradient)

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25
Q

what does the levelling off curve on a distance time graph show

A

slowing down (decreasing gradient)

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26
Q

speed = gradient equ

A

change in the vertical / change in the horizontal

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27
Q

what does a velocity time graph show

A

velocity change over time

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28
Q

what does the gradient on a velocity time graph show

A

acceleration

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29
Q

acceleration equ

A

change in velocity / time

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30
Q

what does the flat sections on a velocity time graph show

A

steady speed

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31
Q

what does the steep sections on a velocity time graph show

A

the greater the acceleration or deceleration

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32
Q

what does the curve on a velocity time graph show

A

changing acceleration

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33
Q

what is the area under a velocity time graph

A

distance travelled

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34
Q

what is Newton’s first law

A

if the resultant force on a stationary object is zero, the object will remain stationary. if the resultant force on a moving object is 0 it will carry on moving at the same velocity (same speed and direction)

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35
Q

what is acceleration proportional to

A

resultant force

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36
Q

what is Newton’s second law

A

force = mass x acceleration

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37
Q

why can large decelerations be dangerous

A

can cause serious injuries as it requires a large force

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38
Q

what are some safely features in vehicles and what are they designed to do

A

designed to increase collision times and reduce the force and reduces the risk of injury

e.g.
seat belts stretch slightly
air bags slow you down gradually
crumple zones in a car so a vehicle crumples easily, increasing time to stop

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39
Q

mass

A

the amount of ‘stuff’ in an object, same value anywhere in the universe

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40
Q

is mass scalar or vector

A

scalar

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41
Q

how is mass measured

A

kilograms with a mass balance

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42
Q

weight

A

the force acting on an object due to gravity (pull of the gravitational force on the object)

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43
Q

how is weight measured

A

in newtons using a spring balance or newton meter

44
Q

weight equ

A

mass (kg) x gravitational field strength (N/kg)

45
Q

what is centripetal force

A

force acting on the centre of the circle which keeps it moving in a circle

46
Q

how can you investigate motion

A
  1. measure the mass of the trolley, the unit mass and hanging hook, measure the length of the piece of card
  2. adjust the height of the ramp until the trolley begins to move
  3. mark a line to ensure it travels the same distance every time
  4. hold the trolley at the start line then let go so it starts to roll down the slope
  5. each light gate will record the time when the trolley passes through
  6. that way you can find the acceleration, initial speed and final speed + time
47
Q

what is newtons 3rd law

A

reaction forces are equal and opposite, when 2 objects interact, the forces they exert on each other are equal and opposite

48
Q

momentum equ

A

mass x velocity

p = m x v

49
Q

what does total momentum before =

A

total momentum after

50
Q

force equ

A

change in momentum / time

f = mv - mu / t

51
Q

what is stopping distance

A

the distance covered between the driver first spotting a hazard and the vehicle coming to a complete stop

made up of thinking distance and braking distance

52
Q

what is thinking distance

A

the distance the car travels in the drivers reaction time

53
Q

what is thinking distance made up of

A

reaction time - tiredness, alcohol, drugs and distractions
your speed - faster you go, further you travel

54
Q

what is your braking distance

A

the distance taken to stop once the brakes have been applied

effected by:
your speed
the mass of the car
conditions of the brakes
friction between tyres and road

55
Q

what does the ruler drop test measure

A

a humans reaction time

56
Q

how to perform the ruler drop test

A

drop a ruler facing with 0cm at the bottom with someone’s hand below it, when you let go, the person needs to grab it as fast as possible, the quicker you grab it, the better the number on the ruler, the quicker your reaction time.

57
Q

energy in the cars kinetic energy store =

A

work done by the brakes

1/2 x mass x velocity2 = f x d

58
Q

how is energy transferred

A

between energy stores

59
Q

kinetic

A

anything moving has energy in its kinetic energy store

60
Q

thermal

A

any object, the hotter it is the more energy it has in this store

61
Q

chemical

A

anything that can release energy by chemical reaction
e.g. food, fuel

62
Q

gravitational potential

A

anything in a gravitational field

63
Q

elastic potential

A

anything stretched, like springs and rubber bands

64
Q

electrostatic

A

two charges that attract and repel each other

65
Q

magnetic

A

two magnets that attract or repel each other

66
Q

nuclear

A

atomic nuclei release energy for this store in nuclear reactions

67
Q

kinetic energy equ

A

1/2 x mass x velocity (squared)

68
Q

GPE equ

A

mass x gravitational field strength x change in vertical height

69
Q

what is conservation of energy

A

energetic can be stored, transferred and dissipated but can never be created or distorted - total energy of a closed system has no net change

70
Q

what are the 4 ways energy can be transferred between stores

A

mechanically
electrically
heating
radiation

71
Q

how can you mechanically transfer energy

A

a force acting on a object
e.g. pushing, stretching, squashing

72
Q

how can you electrically transfer energy

A

a charge doing work

73
Q

how can you by heating transfer energy

A

energy transferred from a hotter object to a cooler one

74
Q

how can you by radiation transfer energy

A

energy transferred by waves

75
Q

efficiency

A

a comparison of the energy output to the energy input in a given system.

76
Q

when is energy useful

A

only when it is transferred from one store to a useful store

77
Q

total energy input equ

A

useful energy output + wasted energy

78
Q

efficiency equ

A

useful energy transferred by device (J) / total energy supplied to device (J)

79
Q

what diagrams can you use to show efficiently

A

sankey diagram

80
Q

what can reduce energy transferred by friction

A

lubrication - makes object flow easily when you coat them - usually liquids

81
Q

what reduces the rate of energy transfer by heating

A

insulation

82
Q

what is conduction

A

when one side of an object is heated, the particles in the hotter part vibrate more and collide with each other.

this transfers energy from their kinetic stores to other particles which then vibrate faster

83
Q

what are the 2 types of resources

A

non renewable
renewable

84
Q

examples of non renewable resources

A

fossil fuels
nuclear fuel

85
Q

positive facts about non renewable resources (fossil fuels)

A

reliable
plenty around for current demand
easy to extract and relatively cheap to build and run fossil fuel power plants

86
Q

negative facts about non renewable resources (fossil fuels)

A

slowly running out
cause environmental problems - release greenhouse gases (co2) contributes to global warming
burning coal also releases sulfur dioxide, causing acid rain
oil spillages cause problems to plants and animals in and around the sea

87
Q

postive facts about non renewable resources (nuclear power)

A

clean
provide most of worlds energy
always have fuel in stock - response quickly - releases more energy

88
Q

negative facts about non renewable resources (nuclear power)

A

slowly running out
expensive to build and safely decommission
very dangerous and difficult to dispose of

89
Q

examples of renewable energy resources

A

bio fuels
wind
solar
hydro electricity
tides

90
Q

positives of renewable resources

A

will never run out
do less damage than nonrenewable resources

91
Q

negatives of renewable resources

A

still do damage to the environment and they don’t provide much energy
unreliable as they depend on the weather

92
Q

biofuels

A

they are carbon neutral either solid, liquid or gas renewable resources made from either plant products or animal waste which is burnt to produce electricity or run cars the same way as fossil fuels

93
Q

wind power facts

A

wind turbines have a generator inside, wind rotates the blade, generator produces electricity, there’s no pollution

94
Q

advantages of wind power

A

running costs are minimal

95
Q

disadvantages of wind power

A

initial costs are high
lots of them are needed - they can be noisy and eyesore
only work when it’s windy, can’t always supply electricity or respond to high demand

96
Q

solar cells

A

made from materials that use energy transferred by light to create an electric current which are used to power satellites used in remote places

97
Q

solar cell advantages

A

no pollution
no running costs
suitable for sunny locations

98
Q

solar cells disadvantages

A

initial costs are high
small scale
can’t create energy at night or increase production when there is high demand

99
Q

hydroelectricity

A

involves flooding a valley by building a big dam, rainwater is caught and allowed through turbines

100
Q

hydroelectricity advantages

A

no pollution
can immediately respond to increased electricity demand
running costs are low
reliable

101
Q

hydroelectricity disadvantages

A

big impact on environment due to flooding can cause loss of habitat
initial costs are high

102
Q

tidal barrages

A

big dams built across river estuaries with turbines in them, the tide fills up the estuary, water is then let out at a controlled speed to generate electricity

103
Q

tidal barrages advantages

A

no pollution
pretty reliable
no fuel costs
minimal running costs

104
Q

tidal barrages disadvantages

A

can spoil view
affect boat access
initial costs are high
hard to control natural water levels

105
Q

what do we currently depend on

A

fossil fuels
20th century - electricity hugely increased
21st century - making appliances maker efficient

106
Q

why are energy resources chosen

A

for their effect on the environment

107
Q

what is the use of renewables limited by

A

reliability
money

physics (7 decks)

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