## A 90 kg person is sitting in a boat at rest with a mass of 100 kg?

Question

The person throws a stone of mass 5 kg at 4 m/s horizontally in the north direction. The velocity of the person and the boat after throwing the stone is ?

I know it will be on the opposite direction but I don’t know how to find the magnitude

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General Physics
4 years
1 Answer
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## Answer ( 1 )

Let’s determine the momentum of the stone.

M = 5 * 4 = 20

Let’s determine the sum of mass of person and boat.

Mass = 90 + 100 = 190 kg

Let v be the velocity of the person and boat after the stone is thrown.

M = 190 * v

Let’s set this equal to the increase of stone’s momentum.

190 * v = 20

v = 20 ÷ 190

This is approximately 0.105 m/s.