# P3- Forces for Transport

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• Created by: Janviixo
• Created on: 16-02-16 12:43
What is the formula for distance?
distance= speed x time
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What is the formula for average speed?
average speed = (u + v) / 2
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What equation do you get when you add the distance and average speed formulas together?
distance = (u + v) / 2 (x t)
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On a distance-time graph what does the gradient show?
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What do curves show on a distance-time graph?
acceleration or deceleration
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What is the formula for acceleration?
acceleration = change in speed / time taken
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What is acceleration measured in?
m/s
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On a speed-time graph what does the gradient show?
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How do you work out the distance on a speed-time graph?
calculate the area of the section under the graph to find the distance
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What is the difference between speed and velocity?
speed is how fast something is going and velocity is speed in a given direction
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Define relative velocity
the difference between two velocities
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What force makes all things accelerate to the ground?
Gravity
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What is the value of acceleration due to gravity on Earth?
10 m/s or 10 N/kg
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Define mass
mass is just the amount of 'stuff' in an object
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Define weight
weight is caused by the pull of gravity, it is a force measured in newtons
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What is the formula for weight?
weight = mass x gravitational field strength
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Name 6 different forces
1) gravity/ weight- down 2) Reaction force 3) Thrust/ Push/ Pull- engine speeding up 4) Friction/ Drag- slows down 5) Lift- wing 6) Tension- rope or cable
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Why are all forces balanced on a stationary object?
gravity is acting downwards causing reaction force to push up
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What happens in terms of forces during a steady horizontal speed?
the forces are in balance, if there was an unbalanced force you'd get acceleration
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What direction does friction act on a moving object?
acts in direction that opposes direction
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Name 3 ways in which friction occurs
1) between solid surfaces which are gripping 2) between solid surfaces which slide 3) resistance/drag from fluids
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How can you reduce drag?
area and shape should be streamlined, closed windows/roof boxes
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In a fluid, what happens as you increase the speed?
friction (drag) always increases as you increase the speed
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What is terminal speed?
when the maximum speed has been reached- resistance force and acceleration force balanced
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How can a skydiver reduce his terminal speed?
by increasing his surface area which increases drag
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To keep going at a steady speed, what must the resultant force be?
zero
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Name the 5 different forms acceleration can take
starting, stopping, slowing down, speeding up and changing direction
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What is the formula for force?
force= mass x acceleration
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How can you find your stopping distance?
stopping distance = thinking distance + braking distance
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Define thinking distance
the distance the car travels in the time it takes for the drive to notice the hazard and applying the brakes
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Name 4 things that affect you thinking distance
speed, drugs, alcohol, lack of concentration, tiredness
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Define braking distance
the distance taken to stop once the brakes have been applied
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Name the 4 factors that affect the braking distance
1) Speed 2) heavily loaded vehicles 3) condition of brakes 4) grip- roads, weather, tyres
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What does speed have a bigger effect on? Braking or Thinking distances?
Braking distance
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What relationship does a cars speed have on the thinking distance?
Linear relationship
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What relationship does a cars speed have on the braking distance?
Squared relationship
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What is the formula for momentum?
momentum = mass x velocity
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What causes a change in momentum?
when a force acts on an object
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What is the formula for a force acting on an object?
force acting = change in momentum / time taken for change to happen
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What is the significance of safety features in a car?
they increase the collision time and reduce deceleration .:. reducing injury
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Name 3 safety features you may find in a car
1) Crumple zones- absorb kinetic energy 2) Seat belts- stretch, reducing force on chest 3) Air bags- slow you down gradually
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What are ABS brakes? Why are they used?
Anit-lock Braking System Brakes: automatically pump on and off to stop wheels locking, shorter breaking distance
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What is the formula for work done?
work done = force x distance
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What is gravitational potential energy?
it is the energy that something has because of its height above the ground
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What formula can you use to find gravitational potential energy?
G.P.E. = mass x gravitational field strength x height
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What is the formula for kinetic energy?
kinetic energy= 0.5 x mass x speed
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What happens to the K.E. when you double the mass?
kinetic energy also doubles
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What happens to the K.E. when you double the speed?
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What formula shows that a falling object coverts G.P.E into K.E.?
kinetic energy gained = gravitational potential energy lost
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Define power
it is a measure of how quickly work is being done
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What is the formula for power?
power = work done/ time taken
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What is power measured in?
Watts or J/s
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What is the formula for power in terms of speed and force?
power= force x speed
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Why do more larger and powerful engines have a high fuel consumption?
it transfers more energy from its fuel per second
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Define fuel consumption
the distance travelled using a certain amount of fuel
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What is fuel consumption usually measured in?
miles per gallon (mpg) or litres per 100km (l/100km)
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Name 5 things that a car's fuel consumption may depend on
1) size of engine 2) speed of car 3) mass of car 4) road conditions 5) how car is driven
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Name 2 disadvantages of using fossil fuels in a car
1) causes environmental issue e.g. acid rain and climate change 2) non-renewable so they'll eventually run out
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What are biofuels?
they are made from plants and organic waste, they're also renewable
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Name an advantage of switching from fossil fuels to biofuels?
the overall carbon dioxide emissions could be reduced
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Explain how electric cars cause pollution?
Electric cars need to be charged with electricity which most likely comes from power stations that pollute
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Name an alternative to electric cars that doesn't cause pollution
solar panels on cars
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What are 3 disadvantages of using electric cars or solar panels?
1) they're expensive to make and buy 2) pollution is created during their production 3) electric cars have limited performance
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## Other cards in this set

### Card 2

#### Front

What is the formula for average speed?

#### Back

average speed = (u + v) / 2

### Card 3

#### Front

What equation do you get when you add the distance and average speed formulas together?

### Card 4

#### Front

On a distance-time graph what does the gradient show?

### Card 5

#### Front

What do curves show on a distance-time graph?