Understanding how to approach exam questions helps to boost exam performance. Questions will include multiple choice, descriptions and explanations, using mathematical skills, and extended writing.

Part of

These are similar to one and two mark questions but you will be expected to write in more depth for three and four mark questions.

Three and four mark questions usually require longer answers.

The answers here give lists of valid points that could be included in your answer.

*This page contains AQA material which is reproduced by permission of AQA.*

- Question
The graph below is the distance-time graph of a car:

Explain what the graph shows about the motion of the car between point A and point E.

You should use values from

**the graph**in your answer.**[4 marks]**There are lots of things that could be said about this graph by describing the types of motion, the gradients of the lines, calculating the speeds or comparing one section to another.

At least

**four**of the following points should be made:- between A and B the car is moving from the origin
- the gradient of the line shows it's moving at a constant speed
- speed between these points is: 250 ÷ 20 = 12.5 m/s
- between B and C the car is stationary/not moving
- because the graph is flat between these points
- showing that the car's speed is 0 m/s
- between C and D car is moving further from the origin
- at a constant speed
- speed is 250 ÷ 20 = 12.5 m/s
- movement between these points is the same as at A-B
- because the gradient is the same
- between D and E the car moves towards origin
- at a constant speed
- speed is 500 ÷ 30 = 16.7 m/s
- gradient between D and E shows that car moves faster or at a greater speed than between any other points

[4]

- Question
The figure below shows two students investigating reaction time:

Student

**A**lets the ruler go.Student

**B**closes her hand the moment she sees the ruler fall.This investigation can be used to find out if listening to music changes the reaction times of a student.

Explain how.

**[4 marks]**- measure the distance the ruler falls before being caught
- the greater this distance, the greater the reaction time
- repeat measurements and calculate a mean
- repeat several times with the student listening to music (through earphones)
- calculate a mean
- a large difference between the two means would show that music affects reaction time

[4]

You will need to describe the steps to be carried out in the investigation and how to interpret the results. Steps should be logically ordered so that they could be followed by someone else.

- Question
A swimmer dives into the water from a stationary boat.

As the swimmer dives forwards, the boat moves backwards.

Use the idea of conservation of momentum to explain why the boat moves backwards.

**[4 marks]**momentum before = momentum after [1]

Before diving in, the momentum of the diver and boat is zero. After diving, the diver has forwards momentum [1]. Therefore the boat has equal backwards momentum [1].

Conservation of momentum means that the total momentum before an event/interaction will be equal to the total momentum afterwards [1].

- Question
A car driver sees a fallen tree lying across the road ahead and makes an emergency stop.

The braking distance of the car depends on the speed of the car.

For the same braking force, explain what happens to the braking distance if the speed doubles.

You should refer to kinetic energy in your answer.

**[4 marks]**Doubling the speed of the car increases its kinetic energy by four times [1]. This means that the brakes must do four times as much work to bring the car to a stop [1]. Since the maximum braking force is constant [1], the car must travel four times further whilst the brakes are being applied [1].

A strong answer will be clearly worded with good use of scientific key words. It may include the following points:

- doubling speed increase the kinetic energy
- kinetic energy increases by a factor of four
- work done (by brakes) to stop the car increases
- work done increases by a factor of four
- work done is force × distance and braking force is constant
- so if work done increases by four then the braking distance must increase by four