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MYP Physics · 03 · extended response

Grip, rolling resistance, and a wheelchair tyre

Forces · Original GioPhysics question with a detailed, mark-by-mark answer guide.

Demand
discriminating
Marks
8
Topics
3
Answer
Complete
extended response8 marks

A school is choosing wheelchair tyres. Tyre P needs an average push of 18 N on a smooth floor and 31 N on carpet; it stops in 1.8 m on a wet ramp. Tyre Q needs 23 N on the floor and 38 N on carpet; it stops in 1.2 m on the same wet ramp. Both meet the load rating.

  1. a

    Interpret Explain what the push-force and stopping-distance evidence suggests about the two tyres.

    3 marks
  2. b

    Recommend Recommend a tyre for a route that includes carpet and a short wet ramp. Justify the choice using physics and user needs.

    3 marks
  3. c

    Propose Propose one further test needed before a final purchasing decision and explain why it matters.

    2 marks
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Answer overviewKey answer: Explains that P has lower rolling resistance because it requires less force on both surfaces. Explains that Q provides greater wet-ramp grip because its stopping distance is shorter. Recognises that the evidence shows a trade-off rather than one tyre being best in every respect.
01

a

3 marks

Interpret Explain what the push-force and stopping-distance evidence suggests about the two tyres.

How to approach it

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. 1

    Explains that P has lower rolling resistance because it requires less force on both surfaces.

  2. 2

    Explains that Q provides greater wet-ramp grip because its stopping distance is shorter.

  3. 3

    Recognises that the evidence shows a trade-off rather than one tyre being best in every respect.

02

b

3 marks

Recommend Recommend a tyre for a route that includes carpet and a short wet ramp. Justify the choice using physics and user needs.

How to approach it

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. 1

    Makes a clear recommendation that is consistent with a stated priority.

  2. 2

    Uses at least two relevant numerical comparisons from the evidence.

  3. 3

    Balances effort or fatigue against control and stopping safety for the user.

03

c

2 marks

Propose Propose one further test needed before a final purchasing decision and explain why it matters.

How to approach it

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. 1

    Proposes a relevant controlled test such as durability, side-slope grip, different user loads, or repeated wet braking.

  2. 2

    Connects the test to a limitation in the current evidence or a real user requirement.

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