motion, forces and conservation of energy Flashcards
1
Q
what do vectors have
A
magnitude and direction
2
Q
what do scalars have
A
just magnitude
3
Q
examples of vector quantities
A
force, velocity, displacement, weight, acceleration, momentum
4
Q
examples of scalar quantities
A
speed, distance, mass, energy, temperature, time
5
Q
what is distance
A
how far the object moved
6
Q
what is displacement
A
the distance and direction in a straight line from the starting point
7
Q
what is speed
A
how fast your going
8
Q
what is velocity
A
speed in a given direction
9
Q
walking speed
A
1.4m/s
10
Q
what is running speed
A
3m/s
11
Q
what is the speed of a aeroplane
A
250m/s
12
Q
equation for distance travelled (m)
A
average speed (m/s) x time (s)
13
Q
equation of acceleration
A
v-u (change in velocity: v is final, u is initial) / t
14
Q
what is acceleration
A
change in velocity in a certain amount of time
15
Q
what is deceleration
A
negative acceleration
if something slows down - change in velocity is negative
16
Q
how to estimate acceleration
A
- estimate how long it would take the car to stop
- put these numbers into the accelerating equ
- as the car slowed down, change in velocity and acceleration is negative - car is decelerating
17
Q
another word for constant acceleration
A
uniform acceleration
18
Q
equ for uniform acceleration
A
v (squared) - u (squared) = 2 x a x X (distance)
19
Q
what do distance time graphs show (2)
A
how far something has travelled and the speed of the object
20
Q
what does the gradient on a distance time graph show
A
speed of the object
21
Q
what does the flat section on a distance time graph show
A
where it’s stopped
22
Q
what does the steeper graph on a distance time graph show
A
going faster
23
Q
what does the curves on a distance time graph show
A
acceleration
24
Q
what does the curve getting steeper on a distance time graph show
A
speeding up (increasing gradient)
25
what does the levelling off curve on a distance time graph show
slowing down (decreasing gradient)
26
speed = gradient equ
change in the vertical / change in the horizontal
27
what does a velocity time graph show
velocity change over time
28
what does the gradient on a velocity time graph show
acceleration
29
acceleration equ
change in velocity / time
30
what does the flat sections on a velocity time graph show
steady speed
31
what does the steep sections on a velocity time graph show
the greater the acceleration or deceleration
32
what does the curve on a velocity time graph show
changing acceleration
33
what is the area under a velocity time graph
distance travelled
34
what is Newton’s first law
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)
35
what is acceleration proportional to
resultant force
36
what is Newton’s second law
force = mass x acceleration
37
why can large decelerations be dangerous
can cause serious injuries as it requires a large force
38
what are some safely features in vehicles and what are they designed to do
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
39
mass
the amount of ‘stuff’ in an object, same value anywhere in the universe
40
is mass scalar or vector
scalar
41
how is mass measured
kilograms with a mass balance
42
weight
the force acting on an object due to gravity (pull of the gravitational force on the object)
43
how is weight measured
in newtons using a spring balance or newton meter
44
weight equ
mass (kg) x gravitational field strength (N/kg)
45
what is centripetal force
force acting on the centre of the circle which keeps it moving in a circle
46
how can you investigate motion
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
what is newtons 3rd law
reaction forces are equal and opposite, when 2 objects interact, the forces they exert on each other are equal and opposite
48
momentum equ
mass x velocity
p = m x v
49
what does total momentum before =
total momentum after
50
force equ
change in momentum / time
f = mv - mu / t
51
what is stopping distance
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
what is thinking distance
the distance the car travels in the drivers reaction time
53
what is thinking distance made up of
reaction time - tiredness, alcohol, drugs and distractions
your speed - faster you go, further you travel
54
what is your braking distance
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
what does the ruler drop test measure
a humans reaction time
56
how to perform the ruler drop test
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
energy in the cars kinetic energy store =
work done by the brakes
1/2 x mass x velocity2 = f x d
58
how is energy transferred
between energy stores
59
kinetic
anything moving has energy in its kinetic energy store
60
thermal
any object, the hotter it is the more energy it has in this store
61
chemical
anything that can release energy by chemical reaction
e.g. food, fuel
62
gravitational potential
anything in a gravitational field
63
elastic potential
anything stretched, like springs and rubber bands
64
electrostatic
two charges that attract and repel each other
65
magnetic
two magnets that attract or repel each other
66
nuclear
atomic nuclei release energy for this store in nuclear reactions
67
kinetic energy equ
1/2 x mass x velocity (squared)
68
GPE equ
mass x gravitational field strength x change in vertical height
69
what is conservation of energy
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
what are the 4 ways energy can be transferred between stores
mechanically
electrically
heating
radiation
71
how can you mechanically transfer energy
a force acting on a object
e.g. pushing, stretching, squashing
72
how can you electrically transfer energy
a charge doing work
73
how can you by heating transfer energy
energy transferred from a hotter object to a cooler one
74
how can you by radiation transfer energy
energy transferred by waves
75
efficiency
a comparison of the energy output to the energy input in a given system.
76
when is energy useful
only when it is transferred from one store to a useful store
77
total energy input equ
useful energy output + wasted energy
78
efficiency equ
useful energy transferred by device (J) / total energy supplied to device (J)
79
what diagrams can you use to show efficiently
sankey diagram
80
what can reduce energy transferred by friction
lubrication - makes object flow easily when you coat them - usually liquids
81
what reduces the rate of energy transfer by heating
insulation
82
what is conduction
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
what are the 2 types of resources
non renewable
renewable
84
examples of non renewable resources
fossil fuels
nuclear fuel
85
positive facts about non renewable resources (fossil fuels)
reliable
plenty around for current demand
easy to extract and relatively cheap to build and run fossil fuel power plants
86
negative facts about non renewable resources (fossil fuels)
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
postive facts about non renewable resources (nuclear power)
clean
provide most of worlds energy
always have fuel in stock - response quickly - releases more energy
88
negative facts about non renewable resources (nuclear power)
slowly running out
expensive to build and safely decommission
very dangerous and difficult to dispose of
89
examples of renewable energy resources
bio fuels
wind
solar
hydro electricity
tides
90
positives of renewable resources
will never run out
do less damage than nonrenewable resources
91
negatives of renewable resources
still do damage to the environment and they don’t provide much energy
unreliable as they depend on the weather
92
biofuels
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
wind power facts
wind turbines have a generator inside, wind rotates the blade, generator produces electricity, there’s no pollution
94
advantages of wind power
running costs are minimal
95
disadvantages of wind power
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
solar cells
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
solar cell advantages
no pollution
no running costs
suitable for sunny locations
98
solar cells disadvantages
initial costs are high
small scale
can’t create energy at night or increase production when there is high demand
99
hydroelectricity
involves flooding a valley by building a big dam, rainwater is caught and allowed through turbines
100
hydroelectricity advantages
no pollution
can immediately respond to increased electricity demand
running costs are low
reliable
101
hydroelectricity disadvantages
big impact on environment due to flooding can cause loss of habitat
initial costs are high
102
tidal barrages
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
tidal barrages advantages
no pollution
pretty reliable
no fuel costs
minimal running costs
104
tidal barrages disadvantages
can spoil view
affect boat access
initial costs are high
hard to control natural water levels
105
what do we currently depend on
fossil fuels
20th century - electricity hugely increased
21st century - making appliances maker efficient
106
why are energy resources chosen
for their effect on the environment
107
what is the use of renewables limited by
reliability
money
