Physics · May / June 2021 · Paper 42 · Question 3
0625
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The question as text
Fig. 3.1 shows water flowing at very slow speed over a cliff edge. water rocks 15 m cliff edge Fig. 3.1 The water falls 15 m onto the rocks below.
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3(a)[4]
(PE loss =) mgh AND (KE gain =) ½ mv2
PE (loss) = KE (gain)
alternative route 1 for 1st two m.p.s
v2 = u2 + 2as
u = 0
alternative route 2 for 1st two m.p.s
s = ut + 0.5at2 OR h = 0.5gt2
u = 0 AND t = √3 OR 1.73
v2 (= 2gh) = 2 × 10 × 15 OR v2 = 300 OR v = 10√3 OR v = 10 × 1.73
{v = 17 m / s AND v2 = 300 or v = 10√3} OR v = 17.3(2) m / s
3(b)[3]
(F =) change of p / (change of) time OR rate of change of momentum
(F =) 30 × 17.32
(F =) 520 N
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