A decorator uses a sanding block to smooth a wooden floor by pushing it horizontally across the surface. Explain why work is done against friction and describe the energy transfer that takes place.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A force is applied to the sanding block in the direction of its motion.
Friction acts opposite to the motion, opposing the block’s movement.
Work is done because the applied force moves the block through a distance: W = F × d.
This work against friction is converted into thermal energy, raising the temperature of the block and floor.
Friction acts opposite to the motion, opposing the block’s movement.
Work is done because the applied force moves the block through a distance: W = F × d.
This work against friction is converted into thermal energy, raising the temperature of the block and floor.
Examiner tips
- Use the exact wording ‘force is applied in the direction of motion’ and ‘friction acts opposite to the motion’.
- Show the work formula W = F × d and state that the work is against friction.
- Explain the energy transfer as conversion to heat, not just ‘energy’.
- Keep the answer short – one sentence per point.
Common mistakes
- Confusing the direction of the applied force with the direction of friction.
- Failing to mention that the work is against friction, not just any work.
- Not specifying that the energy becomes thermal (heat).
Mark scheme (4 marks)
- A force is applied to the sanding block in the direction of motion / along the line of action of the force
- Friction acts in the opposite direction to the motion / opposes the movement of the sanding block
- Work is done because a force causes the block to move through a distance / work done = force × distance moved in the direction of the force
- Work done against friction causes the kinetic energy of the decorator / block to be transferred to thermal energy (heat) in the block and floor / causes a rise in temperature
Key terms in this question
Related
- All AQA GCSE Physics (8463) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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