Question

Q. A boy of 50kg hops with a horizontal velocity of 5m/s on stationary skateboard. The skateboard weights 4 kg . Find the velocity when the board starts rolling.​

Answer 1

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Momentum Problem

Given:

m1 = 50 kg

v1 = 5 m/s [E]

m2 = 20 kg

v2 = 1.5 m/s [E]

v3 = final velocity

Foemula:

m1v1 + m2v2 = (m1 + m2) x v3

We need to find v3

v3 = (m1v1 + m2v2) / (m1 + m2)

= (50x5 + 20x1.5) / (50 + 20)

= 280 / 70

= 4 m/s [E]

The final velocity is 4 m/s [E].

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reffer to the attachment

Therefore, the skateboard starts rolling at the speed of 4.62 m/s.