Stopping distances

Question 1

What is thinking distance?

Answer 1

distance travelled by a vehicle in the time it take the driver to react

for a vehicle moving at constant speed, v

the thinking distance s₁ = vt_{<span>0</span>}

t_o = reaction time

Question 2

What affects thinking distance?

Answer 2

alcohol, drugs and distraction

why breathalyser tests are used and phones are banned?

Question 3

What is braking distance?

Answer 3

distance travelled by a car in the time it takes to stop safely, from when the brakes are first applied

assum constant deceleration, a, to zero speed, u

s₂ = u² / 2a

since u² = 2as₂

Question 4

What is stopping distance?

Answer 4

thinking distance + braking distance

ut₀ + u² / 2a

Question 5

What is an anti-lock brake system?

Answer 5

consists of a speed sensor on each whell linked to a centra electronic control unit that controls hydreaulic valves in the brake system

if a wheel locks when the brakes are applied, the control unit senses the wheel is rotating more slowly than the other wheels - valves are activated, so the brake pressure on the wheel is reduced

prevents skidding

Question 6

How is friction tested?

Answer 6

friction between the underside of a block and the surface it is on

pull the block with increasing force until it slides

the limiting frictional force on the block is equal to the pull force on the block just before sliding occurs

depends on weight

Question 7

What does the braking distance depend upon?

Answer 7

speed

road condition

tyre condition

Question 8

How is braking done safely on an icy / greasy surface?

Answer 8

brakes applied more slowly to prevent skidding

friction is reduced

therefore braking distance is longer

Question 9

Why are treads important?

Answer 9

have to be depth, otherwise any grease or water on the road reduces friction greatly