Lesson 9: Stopping Distance

Question 1

What is the “stopping distance” of a vehicle?

Answer 1

• The stopping distance of a vehicle is the sum of the thinking + braking distance.

Question 2

What is the braking distance?

Answer 2

• Distance vehicle travels under the braking force.

Question 3

What is the thinking distance?

Answer 3

• Distance the vehicle travels during the driver’s reaction time.

Question 4

True or False

For any value of braking force, the greater the speed of the vehicle, the greater the stopping distance.

Answer 4

• False.
• For a GIVEN BRAKING FORCE, the greater the speed of the vehicle, the greater the stopping distance.

Question 5

If a car is travelling 20mph, what is the estimated value for the car’s stopping distance?

Answer 5

• 12m

Question 6

If a car is travelling 30mph, what is the estimated value for the car’s stopping distance?

Answer 6

• 23m

Question 7

If a car is travelling 40mph, what is the estimated value for the car’s stopping distance?

Answer 7

• 36m

Question 8

What is the range for typical values of reaction time?

Answer 8

Between 0.2s and 0.9s.

Question 9

What 4 things can affect a driver’s reaction time?

Answer 9

• Tiredness.
• Drugs.
• Alcohol.
• Distractions (ie. use of phone)

Question 10

What is a method to measure human reaction times? If the ruler falls quite far what does this say about the person’s reaction time?

Answer 10

• Person 1 holds ruler.
• Person 2 gets ready to catch ruler.
• Person 1 drops ruler randomly.
• Person 2 cataches the ruler
• If ruler falls quite far down before caught, this says that this person has quite a long reaction time.
• By looking at distance ruler fell - we can look up reaction times in a table.

Question 11

What 3 main things affect the braking distance of a vehicle?

Answer 11

1.) Adverse road (rough surfaces.)
2.) Weather conditions.
3.) Poor condition of the vehicle.

Question 12

What is meant by adverse road conditions?

Give two examples…

Answer 12

1.) Wet conditions.
2.) Icy conditions.

Question 13

What SPECIFIC poor condition of the vehicle will lead to an increase in the braking distance?

Answer 13

• Poor condition of brakes and tires.

Question 14

WHY does the braking distance of a vehicle increase when there are wet/ icy conditions on roads?

Answer 14

• There is reduced friction between the tyres and the road.

Question 15

What happens (in terms of energy transfers) when a force is applied to the brakes of a vehicle?

Answer 15

• Force applied.
• Work is done (by the friction force between the brakes and the wheel.)
• This reduces the kinetic energy of the vehicle and the temperature of the brakes increases (ie kinetic energy now stored in thermal energy store of the brakes.)

Question 16

If a car is travelling at a high speed, how does this affect the braking force that needs to be applied to the brakes of car in order for it to stop?

Answer 16

• A GREATER BRAKING FORCE needed to stop the car/ vehicle in a certain distance.

Question 17

What is the issue with a great braking force? Ie. when a vehicle is at a high speed and needs to make a sudden stop?

Answer 17

• Great braking force = greater decceleration of the vehicle.
• Large decceleration may lead to two things: brakes overheating and/or loss of control.

Question 18

What two main things can large deccelerations in a vehicle lead to?

Answer 18

1.) Overheating brakes (as large braking force means large amount of kinetic energy transferred to thermal energy of the brakes.)
2.) Loss of control of the vehicle.