MYP Physics · 04 · extended response
Safer barriers for a skate park
Momentum · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- discriminating
- Marks
- 8
- Topics
- 3
- Answer
- Complete
A 55 kg rider reaches a barrier at 6.0 m s⁻¹ and comes to rest. Barrier X gives an average stopping time of 0.12 s and can be reused after impact. Barrier Y gives 0.30 s but its foam cartridge must be replaced. Both stop the rider over the available distance.
- a
Calculate Calculate the magnitude of the average force on the rider for each barrier.
3 marks - b
Explain Explain physically why Barrier Y produces a smaller average force.
2 marks - c
Evaluate Recommend a barrier and identify one further piece of evidence the park should obtain.
3 marks
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a
Calculate Calculate the magnitude of the average force on the rider for each barrier.
Build a chain of claim, evidence and physics reasoning. Address more than one relevant factor, identify a limitation or assumption, and finish with a conclusion that is conditional on the evidence rather than absolute.
- 1
Calculates momentum change magnitude = 55 × 6.0 = 330 kg m s⁻¹.
- 2
Calculates Barrier X average force = 330 ÷ 0.12 = 2750 N.
- 3
Calculates Barrier Y average force = 330 ÷ 0.30 = 1100 N.
b
Explain Explain physically why Barrier Y produces a smaller average force.
Build a chain of claim, evidence and physics reasoning. Address more than one relevant factor, identify a limitation or assumption, and finish with a conclusion that is conditional on the evidence rather than absolute.
- 1
Both barriers produce the same momentum change for the same rider and approach speed.
- 2
Barrier Y spreads that impulse over a longer time, so the average force is smaller.
c
Evaluate Recommend a barrier and identify one further piece of evidence the park should obtain.
Build a chain of claim, evidence and physics reasoning. Address more than one relevant factor, identify a limitation or assumption, and finish with a conclusion that is conditional on the evidence rather than absolute.
- 1
Makes a justified recommendation that weighs the much lower force from Y against replacement cost or waste, or prioritises another clearly stated constraint.
- 2
Uses the numerical evidence accurately rather than making a general safety claim.
- 3
Requests relevant evidence such as peak force, performance after rain, replacement time, life-cycle cost, or tests across rider masses and speeds.
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