# P3- Forces for Transport

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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?

gradient = speed

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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?

gradient = acceleration

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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?

kinetic energy quadruples

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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?

#### Back

### Card 4

#### Front

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

#### Back

### Card 5

#### Front

What do curves show on a distance-time graph?

#### Back

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