Forces and Braking

Question 1

Stopping distance

Answer 1

The distance travelled between the driver seeing the hazard and the vehicle stopping moving. It is the sum of the thinking distance and the braking distance.

Question 2

Thinking distance

Answer 2

The distance travelled while the driver reacts to seeing the hazard. During this time, the car travels at a constant speed: thinking distance = speed x reaction time.

Question 3

Breaking distance

Answer 3

The distance travelled by the car once the brakes have been applied.

Question 4

Factors affecting thinking distance

Answer 4

Speed
Reaction time of the driver which depends on:
. if the driver is distracted
. if the driver has taken drugs or alcohol
. if the driver is tired

Question 5

Factors affecting braking distance

Answer 5

Speed
Mass of vehicle
Condition of the vehicle including:
. the tread on tyres
. the state of the vehicle’s brakes
The friction between the trees and the road:
. if the road is icy
. if the road is wet / has oil spilt on

Question 6

Formula to calculate stopping distance

Answer 6

Stopping distance = thinking distance + braking distance

Question 7

Are speed and thinking distance directly proportional?

Answer 7

Yes. When the speed doubles, the thinking distance also doubles. This is expected because distance travelled = speed x time and reaction time is constant.

Question 8

Are speed and braking distance directly proportional?

Answer 8

No. When the speed doubles, the braking distance more than doubles

Question 9

Is a smaller or a larger force needed to decelerate a larger mass?

Answer 9

Larger