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Physics · May / June 2021 · Paper 41 · Question 1

0625

As printed in the paper

The question as text

A skydiver of mass 76 kg is falling vertically in still air. At time t = 0, the skydiver opens his parachute. Fig. 1.1 is the speed–time graph for the skydiver from t = 0. 0 0 1 2 3 4 5 6 20 40 60 t / s speed m / s Fig. 1.1

Read automatically from the paper; the printed page above is exact.

Show the answer and mark scheme

  • 1(a)(i)[2]

    any value from 35 to 43 m / s2

    (a =) (v – u) / t in any form or gradient (of line) or (58 – 50) / 0.20 or equivalent values from the graph

  • 1(a)(ii)[3]

    3800 N

    (F =) ma in any form or ∆p / ∆t in any form

    or 76 × candidate’s 1(a)(i)

    or 760 seen

    76 × candidate’s 1(a)(i) evaluated or 76 × (candidate’s 1(a)(i) + 10) or 76 × (candidate’s 1(a)(i))+ 760

  • 1(b)[3]

    (deceleration because) upward force greater than weight or upward resultant force

    air resistance decreases (with decreasing speed / with time)

    or deceleration decreases or resultant (upward) force decreases

    (until / finally) weight equals air resistance or forces balance or at terminal / constant velocity / speed

  • 1(c)[2]

    at zero speed there is no air resistance

    weight / downwards force is (still) acting or there is (now) a resultant force (downwards at zero speed)

    OR

    forces balance at a speed greater than zero

    speed cannot decrease / no deceleration once forces balance

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