# Forces of Transport P4

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• Created on: 20-04-12 07:25

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Forces of Transport (P3)
Speed
Speed is measured in metres per second (m/s), kilometres per hours (km/h) or
miles per hour (mph).
To wok out the speed of any moving object we need to know two things:
The distance it travels.
The time taken to travel the distance.
Then calculate the speed of the object using the following equation:
The faster the speed of on object, the greater the distance it travels in a
particular time.
The faster the speed of an object, the shorter the time it takes to travel
a particular distance.
Speed cameras generally take two pictures of a vehicle, one a certain amount
of time after the other. The position of the vehicle in relation to the distance
markings on the road in the two pictures can be used to calculate the speed of
the vehicle, using this formula...
Measuring Acceleration
1

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The acceleration of an object is the change in speed per second. In other
words, it is a measure of how quickly an object speeds up or slows down.
Acceleration has only one unit: metres per second per second (m/s2).
To work out the acceleration of any moving object we need to know two
things:
The change in speed.
The time taken for this change in speed.…read more

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Stopping Distance
The stopping distance of a vehicle depends on...
The thinking distance- the distance travelled by the vehicle form the
point the driver realises he need to brake to when he applies the brakes
The braking distance- the distance travelled by the vehicle form the
point the driver applies the brakes to the point at which the vehicle
actually stops.
The thinking distance is increased if...…read more

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The amount of work done depends on...
The size of the force in Newton's
The distance the object is moved in metres.
Power
Power is a measure of how quickly work is done. The unit of power is the watt,
W.
Some cars have much higher power ratings than others and they have may also
use far more fuel. High fuel consumption is expensive for the driver and is also
damaging to the environment.…read more

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The energy required to increase the kinetic energy
The energy required to work against friction
Driving style and speed
Road conditions.
Car safety features
Modern cars have safety features that absorb energy on collision including...
Seatbelts- to prevent the people in the car from being propelled out of
the windscreen if the car comes to a sudden halt.
Air bags- to cushion the impact for the driver and front passenger.
Brakes- to reduce the speed of the car by transferring kinetic energy to
heat energy.…read more

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Adjustable seating allows all drivers to obtain a comfortable position in
which they can reach the steering wheel and control pedals easily.
Reducing Stopping Forces
The stopping forces experienced by the people in the car in a collision can be
reduced by...
Increasing the stopping or collision time
Increasing the stopping or collision distance
Decelerating.
All of the safety features perform one or more of the above tasks (passive
safety features).…read more

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Parachutes are designed to have a larger surface area to increase air
resistance.
Roof boxes on cars may provide useful luggage space but they increase
air resistance.
Deflectors on lorries and caravans will reduce air resistance.
Sports cars are wedged- shaped to reduce air resistance.
When a skydiver jumps out an aeroplane, the speed of his descent can be
considered in two separate parts; before his parachute opens and after his
parachute opens.…read more

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Gravitational Potential Energy & Kinetic Energy
When an object falls, its gravitational potential energy is transferred to kinetic
energy. There are many theme park rides which use this transfer of energy.
1) On most roller-coasters, the cars start high up with a lot of gravitation
potentials energy.
2) As the cars drop, the gravitational potential energy is gradually kinetic
energy.
3) The car reaches its highest speed, maximum kinetic energy, at the
bottom of the slope.…read more

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