Forces and Motion

Question 1

What do forces cause things to do?

Answer 1

• speed up
• slow down
• stay at the same speed.

Question 2

equation for force

Answer 2

force = mass × acceleration

Question 3

Describe thinking distance

Answer 3

• the distance traveled between the need for

braking occurring and the brakes starting to act.

Question 4

Describe braking distance

Answer 4

• the distance taken to stop once the brakes have

been applied

Question 5

Describe stopping distance

Answer 5

thinking distance + braking distance

Question 6

Explain why thinking, braking and stopping distances

are significant for road safety

Answer 6

Drivers have an increased risk of an accident if they are driving too quickly for the road conditions. Speed limits are a way to make drivers go no faster than is thought to be safe for normal conditions on a particular road.
It is especially dangerous if a driver drives too close to the vehicle in front. They may be inside the thinking distance and so could not avoid an accident if the vehicle in front ran into problems.

Question 7

Explain how certain factors may increase thinking

distance

Answer 7

• driver tiredness
  • influence of alcohol or other drugs
  • greater speed
  • distractions or lack of concentration

Question 8

Explain how certain factors may increase braking

distance

Answer 8

• road conditions
• car conditions
• greater speed

Question 9

Explain the effects of increased speed on:

• thinking distance
• braking distance

Answer 9

thinking distance – increases linearly
braking distance – increases as a squared
relationship
e.g. if speed doubles braking
distance increases by a factor of four, if speed
trebles braking distance increases by a factor of
nine.

Question 10

Explain the implications of stopping distances in road safety
• driving too close to the car in front (i.e. inside
thinking distance)
• speed limits
• road conditions.

Answer 10

• speed limits, obey the speed limits
• driving too close to other cars, keep distance from the car in front (mote than the stopping distance)
• road conditions, allow extra room between cars, or drive slowly in bad weather or poor road conditions

Question 11

Explain qualitatively everyday situations where
braking distance is changed including:
• friction
• mass
• speed
• braking force.

Answer 11

• the friction between the tyres and the road is decreased
• mass of the vehicle is increased - a loaded vehicle has a higher kinetic energy which increases breaking distance
• the vehicle is travelling faster - higher kinetic energy which increases braking distance
• the braking force is decreased - a smaller force exerted by the break pads on the wheel disks increases the breaking distance