Forces and Motion Flashcards Preview

Physics Module 3 > Forces and Motion > Flashcards

Flashcards in Forces and Motion Deck (11):

What do forces cause things to do?

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


equation for force

force = mass × acceleration


Describe thinking distance

• the distance traveled between the need for
braking occurring and the brakes starting to act.


Describe braking distance

- the distance taken to stop once the brakes have
been applied


Describe stopping distance

thinking distance + braking distance


Explain why thinking, braking and stopping distances
are significant for road safety

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.


Explain how certain factors may increase thinking

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


Explain how certain factors may increase braking

• road conditions
• car conditions
• greater speed


Explain the effects of increased speed on:
- thinking distance
- braking distance

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


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.

- 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


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

- 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