The Equation-free P3 (3)

Question 1

What is stopping distance? Relate to a car.

Answer 1

The stopping distance of a car is the time it takes between the driver to spot the danger and then the car stopping completely.

The time between the driver to act (see the danger, hit the break) and then stop the car completely, is the stopping distance.

(Stopping distance = thinking Distance + braking distance)

Question 2

What are the 2 factors, the stopping distance is affected by?

Answer 2

Thinking distance and stopping distance

Question 3

What is thinking distance?

Answer 3

The distance the car travelled when the driver noticed the hazard and applied the brakes

Question 4

What is the braking distance?

Answer 4

The distance taken to stop the vehicle completely, once the brakes have been applied.

Question 5

What are the 2 factors that affect the Thinking distance of a driver?

Answer 5

-How fast the driver goes

(Even though you have hit the break, the car was still moving really fast towards the hazard)

• Lack of concentration

(Affected by tiredness, drugs, alcohol, distraction, careless attitude.)

Question 6

What are the 4 factors that affect the Braking distance of a car?

Answer 6

1. How fast you are going
   (The faster your going, the longer it takes for you to stop)
2. Heavy vehicles
   (The heavier the vehicle, the longer it takes to stop)
3. Brakes
   (Pressing hard on a brake is more effective than just putting your foot on it)
4. Grip of tyres and road surface.
   (Also weather, icy roads can be a disaster as there is less friction)
   (The less friction, the longer it takes for the car to stop, the greater the braking distance)

Question 7

What minimum depth of tread should all tyres have?

Answer 7

1.6mm

(Gets rid of the water in wet weather conditions, therefore there is enough friction to prevent the tyres from riding on a layer of water)

Question 8

When driving at a speed of 30mph. What would be your thinking and braking distance?

Answer 8

Thinking distance:

9m - (distance you travel when you realised the hazard and hit the brake)

14m - (distance you travelled when you hit the brake and the car completely stopped)

Question 9

Why would it be more dangerous for a car to travel at 70mph rather than 50mph?

Answer 9

50mph:

Thinking distance - 15m
Braking distance - 38m

70mph:

Thinking distance - 21m
Braking distance - 75m!

(If you were driving at a speed of 70mph and there was a car about 70m in front of you, you would DEFINITELY hit it, if you were driving at 50mph though, you wouldn’t have as 15+38= 53m, therefore you would’ve travelled a maximum distance of 53m and not above 70m)

Question 10

Why are speed limits important when considering the stopping distance?

Answer 10

Because speed affects the stopping distance.

Faster speed, longer stopping distance

Question 11

What does speed limits affect the most. Thinking or braking distance?

Answer 11

Braking distance

Question 12

How does speed/thinking distance graph look like?

Answer 12

The relationship between the graph is linear

Means that it is a straight like, y=x

Question 13

How does a speed/braking distance graph look like?

Answer 13

The relationship between the pattern is a curve.

A squared graph where the braking distance is squared and increases faster the more you speed. y=x2

Question 14

What is momentum?

Answer 14

Momentum has size and direction.

The greater the mass and velocity of an object, the greater its momentum

Question 15

What causes a change in momentum?

Answer 15

When a force acts on it

Question 16

How is change in momentum linked to force?

Answer 16

The quicker the change in momentum (like a car crash), the greater the force (an injury caused by a car crash)

Question 17

How can someone be less injured when in a car crash? Use the idea of momentum.

Answer 17

Cars have been designed to slow down when they have a crash. This means the momentum will take longer to change, therefore the force will be smaller and the person will be less injured.

Question 18

What 4 features can help reduce injuries in a car crash?

Answer 18

1. Crumple Zones-

(When the car hits something and the front/back of the car is crushed)

• the car changed shape, increasing the time taken for the car to stop.
• absorbs kinetic energy too

2. Seat belts -

Stretch slightly which reduces the forces acting on the chest
(Needs to be replaced once stretched as they will not be as strong)
-stop people from hitting hard surfaces inside the car

3. Air bags -

Slows you down gradually

4. Roads made safer-

(Crash barriers to escape lanes)
-Collision force is reduced

Question 19

How does ABS Brakes help drivers ?

Answer 19

Anti-lock braking system brakes:

Allows the person to steer (turn) the car when hitting the brake really hard.

(When hitting the brake hard, ORDINARY brakes will fully stop you from steering (turning your car using the steering wheel) therefore you could only go straight.

ABS brakes, locks wheels and unlock them repetitively so that you are able to steer your car and avoid the hazard rather than going straight into it.

Question 20

What do you use to test safety features?

Answer 20

Crash test dummies

Question 21

How do you test a car’s safety features ?

Answer 21

By purposely crashing a car, with a crash test dummy inside it.

Then watching the crash is a slow motion film footage.