Question

since thequestion states that East ispositive, and the fisherman is moving west, then when the fisherman jumps into the rowboat, they will both be moving west. Therefore the velocity should be NEGATIVE.—— Note: Take East as the positive direction. A(n) 86 kg fisherman jumps from a dock into a 129 kg rowboat at rest on the West side of the dock. If the velocity of the fisherman is 3.4 m/s to the West as he leaves the dock, what is the final velocity of the fisherman and the boat? Answer in units of m/s.

Answer 1

Use the principle of conservation of momentum.

P = m*v

Mass of fisherman, m1 = 86 kg

Mass of boat, m2 = 129 kg

Initial velocity of the fisherman, vi = -3.4 m/s (negative sign in the west direction)

Suppose, the final velocity of the fisherman and the boat = vf

Now, initial momentum of the system, Pi = m1*vi

Final momentum of the system, Pf = (m1+m2)*vf

Use conservation of momentum -

Pi = Pf

=> m1*vi = (m1+m2)*vf

=> vf = m1*vi / (m1+m2) = {86*(-3.4)} / (86+129) = -1.36 m/s

So, the final velocity of the fisherman and the boat will be 1.36 m/s in the west direction.