Question Constellation Sign up for free AQA · GCSE · Physics · Higher
Rocket motion after its engine stops
At a height of 40 km, the rocket stopped burning fuel.
The rocket continued upwards to its maximum height of 60 km.
Explain why the velocity of the rocket decreased between a height of 40 km and a height of 60 km.
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Marking points
- 1 Identifies a force opposing the upward motion, such as gravity or air resistance.
- 2 Explains that after fuel burning stops there is no force in the upward direction of motion.
- 3 Concludes that the resultant force is towards Earth, so the rocket decelerates.
Full-mark answer
Once the rocket stops burning fuel, there is no longer a force acting in the upward direction. Gravity acts downwards, opposite to the rocket's motion, so the resultant force is towards Earth and the rocket decelerates.
Why this answer loses marks
It slows down because the fuel ran out.
This does not identify the forces. A complete explanation links the loss of upward thrust to gravity acting downwards and hence a downward resultant force/deceleration.