posted by josh on .
A lumberjack (mass = 98 kg) is standing at rest on one end of a floating log (mass = 270 kg) that is also at rest. The lumberjack runs to the other end of the log, attaining a velocity of +2.9 m/s relative to the shore, and then hops onto an identical floating log that is initially at rest. Neglect any friction and resistance between the logs and the water.
momentum is the same, zero, at all times
assume he runs in -x direction
as he leaves log 1
98*2.9 = 270 vlog1
vlog1 = 1.05 m/s in + x direction
momentum of log 1 = 270*1.05 = 283.5
therefore the momentum of log 2 with the logger now on board must be -283.5
(98+270)Vlog2 = -283.5