Velocity of the canoe?

Question

Blake stands in a canoe in the middle of a lake. The canoe is stationary. Blake holds an anchor with mass 15 kg, then throws it west with a speed of 8 m/s. Blake has a mass of 115 kg and the canoe has a mass of 20 kg.

a. What is the velocity of the canoe after Blake throws the anchor?

b. Later that day, a friend in another canoe uses her paddle to push off against Blake's canoe, giving her canoe a forward velocity of 1 m/s. The combined mass of the friend and canoe is 90 kg. What is the resulting velocity of Blake's canoe?

Answer 1

This is a conservation of momentum problem. The initial momentum of the system is 0. Set the sum of the momentum of the anchor and the man + canoe = 0. Give it a shot!