A 90.kg person is sitting in a boat at rest with a mass of 100 kg.In the boat is a stone with a mass of 5.00 kg.The person throws the stone at 4.00 m/s horizontally in the NORTH direction.The velocity of the person and the boat after the throwing of the stone is
A) 2.00 m/s NORTH.
B) 1.21 m/s SOUTH.
C) 1.21 m/s NORTH.
D) 0.11 m/s SOUTH.
E) 0.11 m/s NORTH.

Question

Quizplus · Accepted Answer

The momentum before and after the throw must be conserved. The initial momentum is zero. After the throw, the momentum of the stone is (5 kg)(4 m/s) = 20 kg·m/s NORTH. To conserve momentum, the boat and person must have an equal and opposite momentum, so (190 kg)(v) = -20 kg·m/s, giving v = -0.11 m/s, which is SOUTH.

A 90kg Person Is Sitting in a Boat at Rest with with a Mass