Stopping distance and road safetyIB MYP Physics: Subtopic test

1. 1
   A driver in Cairo is travelling along a straight road when a child runs out in front of her car. There is a short delay before she presses the brake pedal, and then the car travels further before it stops.

   (a)

   Which expression gives the stopping distance of the car?

   [1 mark]

   • Athinking distance − braking distance
   • Bthinking distance × braking distance
   • Cthinking distance + braking distance
   • Dbraking distance only

   (b)

   Which factor would increase the thinking distance?

   [1 mark]

   • AThe driver is tired
   • BThe tyres are worn
   • CThe road is wet
   • DThe brakes are worn

   (c)

   Explain why drinking alcohol increases the stopping distance of a car.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A driving test centre in Auckland tests a car on a dry, level road. At 10 m/s the car has a braking distance of 12 m when the brakes apply a constant force. A learner driver has the same reaction time of 0.8 s whatever her speed.

   (a)

   The learner drives at 20 m/s instead of 10 m/s. What happens to the thinking distance?

   [1 mark]

   • AIt stays the same
   • BIt halves
   • CIt becomes four times larger
   • DIt doubles

   (b)

   Which quantity is four times larger when the car travels at 20 m/s instead of 10 m/s?

   [1 mark]

   • AThe speed of the car
   • BThe kinetic energy of the car
   • CThe mass of the car
   • DThe thinking distance

   (c)

   Predict the braking distance of the car at 20 m/s on the same road. Explain your prediction in terms of kinetic energy.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Students in Lagos investigate how the road surface affects the braking distance of a model car. The car is released from the same point on a ramp, so it reaches the same speed at the bottom, and then slides to a stop across a flat surface with its wheels locked. The braking distance was 0.90 m on a smooth plastic sheet, 0.50 m on a wooden board, 0.30 m on carpet and 0.20 m on sandpaper.

   (a)

   State the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Describe the trend in the results and explain it. Link your explanation to road safety, and suggest one way to make the results more reliable.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A city council in Nairobi is considering reducing the speed limit on the roads outside schools from 50 km/h to 30 km/h. Cars on these roads already have seat belts, good tyres and good brakes, but crashes outside schools still cause injuries to children.

   (a)

   Explain how a lower speed limit and wearing seat belts each reduce the risk of serious injury, using ideas about stopping distance, kinetic energy and Newton's laws of motion.

   [6 marks]

   (b)

   Discuss and evaluate the council's proposal to reduce the speed limit outside schools.

   [6 marks]

   Total for question 4: 12 marks

End of questions