Flashcards in Stopping Safely Deck (10)

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1

## what should drivers to on the road to avoid and accident

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- leave enough space in front so they could stop safely

- at least equal to the stopping distance for their speed

2

## what happens as the speed of the car increases and why

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- the thinking distance increases at the same rate

- this is because the driver's reaction time stays fairly constant

- but the higher the speed, the further you go in that time

3

## what is the relationship between speed and braking distance

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- if the speed doubles, the braking distance increases by a factor of 4 (2^2)

- and is the speed trebles, the braking distance increases by a factor of 9 (3^2)

4

## how do brakes stop a car

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- the brakes of the car do work on the car's wheels

- this transfers energy from the car's kinetic energy store to the thermal energy store of the brakes

- so to stop a car, the brakes must transfer all its energy

5

## what is the equation which shows the energy transfer from the kinetic energy stores of the car to the thermal energy stores of the brakes

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- energy in the car's kinetic stores = work done by the brakes

- (1/2 x mass x velocity^2 = force x (braking) distance)

6

## what are the estimated masses of cars, single decker buses and a loaded lorry

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- car's mass is 1000kg

- single decker bus is 10,000kg

- loaded lorry is 30,000kg

7

## what is the estimated reaction time of a driver

### 1 second

8

## what does the first part of a thinking and braking distance velocity time graph look like

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- there is a solid block at the beginning

- its area gives the thinking distance

- the length of it on the time axis gives the reaction time

9

## what does the second part of a thinking and braking distance velocity time graph look like

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- a triangle, with the line at the top of the solid block going down into the time axis

- the area of the triangle gives the braking distance

- the gradient (deceleration) shows the maximum force applied by the brakes

10