# Forces doing work - Six-mark questions

Six-mark questions are often the questions that people find the most difficult. In all longer answer questions, but especially the six-mark ones, it is important that you plan your answer and not just rush into it. After all, you would plan an essay or short story before starting. Without a plan it is easy to stray away from the key point and lose marks, get steps in a process in the wrong order or forget key bits of information.

Six-mark questions will start with command words such as 'describe' or 'explain'. The command words 'describe' and 'explain' can be confusing. If you are asked to describe a graph, you will be expected to write about its overall shape, whether it is linear or curved, the slope of gradients etc. If you are asked to explain why a pattern or trend is seen in a graph, you will be expected to use your science knowledge, not just say what you see (which is a description), eg 'The graph shows the number of radioactive nuclei decreases as time increases. It does this because…'.

'Explain how' and 'why' questions often have the word 'because' in their answer. 'Describe' questions don't.

The number of marks per question part is given in this form '[6 marks]'. It is essential that you give as many different points in your answer as possible, linking these together. Often, you will be asked to compare two things: make sure that you include both in your answer, otherwise you are likely to limit your score to two marks out of six marks.

## Sample question 1 - Foundation and Higher

Question

A student stands on the ground with an egg in his hand. He throws the egg vertically upwards. The egg rises to a height of 10 m. Then the egg falls and lands on the ground. Describe the energy changes of the egg during this sequence of events. [6 marks]

Edexcel question courtesy of Pearson Education Ltd.

Chemical energy store to kinetic energy store while the egg is in his hand [1]. Kinetic energy is transferred into gravitational potential while the egg rises [1]. Eventually all kinetic energy has been converted into gravitational potential energy [1]. This is the maximum height [1]. As the ball falls gravitational potential energy is gradually converted into kinetic energy [1]. Some energy will also be converted into thermal energy due to air resistance, but the total amount of energy is conserved [1].

Plan the key points that you should include in your answer. Consider the energy changes at each stage - the initial throw upwards, as the ball moves upwards and then as the ball falls back down.

## Sample question 2 - Foundation and Higher

Question

A racing car is travelling at 80 m/s. It has a kinetic energy of 1.6 MJ. The car brakes to a stop. Beth thinks this shows that the kinetic energy of the racing car has disappeared and this means energy is not conserved. Explain whether Beth is correct. [6 marks]

This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

Energy is always conserved [1], so Beth is wrong [1]. The kinetic energy of the car was transferred into thermal energy [1] of the brakes when the brakes were applied [1]. Since there was 1.6 MJ of kinetic energy of the car, there must be 1.6 MJ of thermal energy [1] in the brakes or the surroundings once the car has stopped [1].

Plan the key points that you should include in your answer. Explain that energy is always conserved and where the kinetic energy of the car has gone.

## Sample question 3 - Foundation and Higher

Question

Kevin pushes his brother Gary on a swing. Kevin then stops pushing Gary. Gary remains on the swing until it slows and stops. Describe the changes in the way energy is stored in this system. [6 marks]

This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

Chemical energy in Kevin is transferred mechanically to the kinetic energy of Gary/the swing [1]. The swing continually transfers energy from kinetic to gravitational potential energy stores [1]. At the top of the swing, all of the energy is stored as gravitational potential energy [1]. At the bottom of the swing, all the energy is stored as kinetic energy [1]. Once Kevin stops pushing, the swing starts to slow down and reach a lower maximum height [1] as energy is transferred to heat in the surroundings due to air resistance and friction [1].

This question is about conservation of energy. Start by thinking about the energy stored at the top of the swing's motion, and how it changes as it goes back and forth. Then add an explanation as to why the swing comes to a standstill.