A peron on a boat with a total mass of M are stationary in the river, the man throws his shoes mass m at a velocity v successive, find the expression for the boat's final velocity.(adsbygoogle = window.adsbygoogle || []).push({});

Here is what I did.

First let u be the velocit of the boat

After the first shoes:

(M + m)u = mv

u = mv(1/(M +m))

After the second shoes:

Change in momentum of the boat = Change in momentum of the shoe

So, Mu'- (M + m)u = mv, but (M + m)u = mv

Therefore Mu' = 2mv and u' = 2mv/M

u + u' = mv(2/M + 1/(M + m)) is the final velocity of the boat.

But the correct answer is mv(1/(M + m) + 1/(M + 2m)), can anyone please tell me where I've got it wrong?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: A Momentum Problem

**Physics Forums | Science Articles, Homework Help, Discussion**