*39.  A girl is skipping stones across a lake. One of the stones accidentally ricochets off a toy boat that is initially at rest in the water (see the drawing). The 0.072-kg stone strikes the boat at a velocity of 13 m/s, 15° below due east, and ricochets off at a velocity of 11 m/s, 12° above due east. After being struck by the stone, the boat’s velocity is 2.1 m/s, due east. What is the mass of the boat? Assume the water offers no resistance to the boat’s motion.

 

 

Considering stone and boat as a single system, momentum is conserved in the x direction.  So

 

 

 

 

 

 

 

 

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This page last updated on January 11, 2020