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Laws of Conservation

Problem 1.159

A raft of mass MM with a man of mass mm aboard stays motionless on the surface of a lake. The man moves a distance 1′1^{\prime} relative to the raft with velocity v′(t)\mathrm{v}^{\prime}(t) and then stops. Assuming the water resistance to be negligible, find: (a) the displacement of the raft 1 relative to the shore; (b) the horizontal component of the force with which the man acted on the raft during the motion.

Reveal Answer
(a) I=−mM+ml′\mathbf{I}=-\frac{m}{M+m} \mathbf{l}^{\prime} (b) F=−mMM+mdv′dt\mathbf{F}=-\frac{m M}{M+m} \frac{d \mathbf{v}^{\prime}}{d t}
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