Question

A fisherman in a boat catches a huge fish with a rod and starts to pull it in. The fish
struggles for a while and then becomes still when it is at a distance of 200 m from the
boat. During this operation, the boat (initially at rest) moves 25 m in the direction of the
fish. If the mass of the boat is 5000 kg, calculate the mass of the fish. Assume that water
exerts no friction.

Answer 1

Solution

The boat move 25m while the fish is being reeled in from 200m.It's a center of mass problem-if the water friction can be ignored then the center of mass of the boat/fish system lies 25m from the initial position ofthe boat.

m1x1 = m2x2 

m2 = $\frac{x1}{x2}$ m1 = $\frac{25}{200}$ 5000 = 625 kg 

Answer = 625 kg