1. The physics of braking In this section you will:-
apply Newton’s law to practical situations
know how the stopping distance can be
affected by the road conditions
understand the processes happening in the
body and how they give rise to the reaction
time

2. the car has a mass of 1.25Tonnes (1250kg)
it decelerates at 2m/s to avoid hitting the
child
work out the braking force using Newton’s
law
1 Applying Newton’s law 2
F = m x a = x =
Click to check your answer

3. the car has a mass of 1.25Tonnes
it decelerates at 2m/s to avoid hitting the
child
work out the braking force using Newton’s
law
1 Applying Newton’s law 2 2
F = m x a = x = m/s

4. 2 Changing the conditions
Unfortunately this morning there was ice on the road. If the
driver avoids skidding he can only use 2000N of braking force.
work out the cars deceleration today.
a = F/m = / =
What difference does this make?
How should the car be driven
differently in icy conditions?

5. 2 Changing the conditions
Unfortunately this morning there was ice on the road. If the
driver avoids skidding he can only use 2000N of braking force.
work out the cars deceleration today.
2 Changing the conditions 2
a = F/m = / = 1.6m/s
What difference does this make? Less force means less deceleration
larger stopping distance
SORRY!
How should the car be driven
differently in icy conditions?
More slowly

6. 3 How it works
Step 1 Light travels to the
driver(she sees the danger)
Step 2 Information sent from
her eyes to the brain
Step 3 Signal sent as a nerve
impulse to the foot
Step 4 Muscles move the
foot to the brake pedal
Step 5 The brake is pressed

7. 1 Explain why it takes time to react
Questions
1 Explain why it takes time to react
2 People often feel perfectly normal after
drinking alcohol. Why is it a bad idea for
people to drink and drive?
3 (a) Explain what happens to the braking
force when the road is icy.
(b) What happens as a result of this change
to the braking force?
Click for the answers

8. 1 Explain why it takes time to react
Answers
1 Explain why it takes time to react
2 People often feel perfectly normal after
drinking alcohol. Why is it a bad idea for
people to drink and drive?
3 (a) Explain what happens to the braking
force when the road is icy.
(b) What happens as a result of this change
to the braking force?
It takes time for the brain to receive and send signals
It takes time to move you foot across and put it on the brake
It slows down their reactions/the thinking distance will be a bigger distance
It has to be smaller otherwise the car will skid
The car will travel a larger distance before it stops

9. END