Physics · May / June 2020 · Paper 42 · Question 2
0625
As printed in the paper
The question as text
Fig. 2.1 shows a train. Fig. 2.1 The total mass of the train and its passengers is 750 000 kg. The train is travelling at a speed of 84 m / s. The driver applies the brakes and the train takes 80 s to slow down to a speed of 42 m / s.
Read automatically from the paper; the printed page above is exact.
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2(a)[3]
impulse OR ∆p = m(v – u) in any form
(impulse =) 750 000 (84 – 42)
(impulse =) 3.2 × 107 N s or m kg / s
2(b)[2]
Ft = impulse OR ∆p in any form
OR (F =) (impulse OR ∆p) / t
(F = 3.2 x 107 / 80 =) 3.9 ×105 N
2(c)[1]
reduces drag / air resistance (experienced by the train) / more streamlined
2(d)[1]
less drag / air resistance (at slower speeds)
2(e)[1]
(maximum) friction (force) between rails and train reduced / train may slide
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