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Forces and Motion

The Stopping Distance of a Car.

The total distance that is needed to stop a moving car
can be divided into two parts called
the thinking distance and the braking distance.

What is the Thinking Distance?

The thinking distance is the distance the car travels
during the driver's reaction time.

The reaction time is the length of time between the
moment when the driver realizes that the car must be stopped
the moment when they apply (put on) the brakes.
The faster the car is travelling,
the further the car moves during the thinking distance.

What Increases the Thinking Distance?

Thinking distance is increased if the reaction time of the driver
gets longer because of tiredness, alcohol (or other drugs)
or distractions. Common distractions include using
a mobile phone or a satellite navigation system (Sat Nav).

What Decreases the Thinking Distance?

The thinking distance can be decreased by using
road signs to warn the driver that they might have to stop soon.
The more alert a driver is, the shorter their reaction time,
the quicker they can apply the brakes
and the smaller is the thinking distance.

The total stopping distance = thinking distance + braking distance.

See the next page for the braking distance.

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