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Force and Laws of Motion
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02/11/2021 4:20 pm
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A boy of mass 50 kg running at 5 m/s jumps on to a 20 kg trolley travelling in the same direction at 1.5 m/s. What is their common velocity?
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02/11/2021 4:24 pm
Mass of the boy, m1= 50 kg
Speed of boy, u1 = 5 m/s
Mass of trolley m2 = 20 kg
Speed of trolley u2 = 1.5 m/s
Combined mass of boy and trolley, m = 20 + 50 = 70 kg
Combined velocity v
Acc. to the law of conservation of momentum
m1u1 + m2u2 = mv
50 x 5 + 20 x 1.5 = 70 x v
v = \(\frac{250 + 30}{70}\) = 4 m/s