Michael C. answered • 02/14/17

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4.9
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PhD with 20 years experience teaching math and applied science

First, you have to have consistency in units

km/h = 1000/3600 m/s

momentum = mass * velocity

a) Total Initial momentum = 900*70*1000/3600 + 60 * 1

= 17,560 kg.m/s

b) momentum is conserved 17,560 = 900*30*1000/3600 + 60v; v = 168 m/s

c) impulse = change of momentum = 60(168-1) =10,020 m.kg/s

d) average force = rate of change of momentum = 10,020/0.4 = 25050 J = 25.05 kJ