Difficult Physics Question: Conservation of Momentum?

I won't do your homework for you, but consider this. The conservation of momentum means that any momentum lost by one object must be gained by some other object that it interacted with. Ignoring the water the log and lumberjack are floating on (which is a big umption, not one that would give accurate results in real life,) any change in the lumberjack's momentum would have to affect the momentum of the first log in the opposite way. Once the lumberjack is on the second log, his momentum would simply be distributed to him and the log. Hope that helps! (If this isn't enough, might I suggest meeting with your teacher for some more help.)