A-level · Quantities & units

Modelling assumptions & SI unitsExam-style questions

What each standard modelling word actually lets you ignore — particle, light, inextensible, smooth, rigid, uniform — so you can read an assumption off a question and know its consequence, the SI units mechanics is built on, and how to answer "state a limitation" by naming what the model leaves out.

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6 questions · A-level level · mark scheme and worked solution on each · no sign-up to try

DifficultyAllLevel 2Level 3
  1. 1
    In mechanics, explain what is meant by modelling a body as a "particle", and give one advantage of doing so.
    Level 2 · 2 marksTry it
  2. 2
    A string is modelled as "light and inextensible". State what each of these assumptions means.
    Level 2 · 2 marksTry it
  3. 3
    State what is meant by modelling a surface as "smooth", and how this affects the forces in a problem.
    Level 2 · 2 marksTry it
  4. 4
    Two particles are connected by a light inextensible string passing over a pulley. Explain why the two particles have the same acceleration.
    Level 3 · 1 markTry it
  5. 5
    State the SI units used for
    (a) force,
    (b) mass and (c) acceleration.
    Level 3 · 3 marksTry it

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