ssm A lumberjack(mass = 98 kg) is standing at rest on one end of a floating log(

Question

ssm A lumberjack(mass = 98 kg) is standing at rest on one end of a floating log(mass = 300 kg) that is also at rest. Thelumberjack runs to the other end of the log, attaining a velocityof +3.7 m/srelative to the shore, and then hops onto an identical floating logthat is initially at rest. Neglect any friction and resistancebetween the logs and the water. (a) What is the velocity of the first log justbefore the lumberjack jumps off? (Indicate the direction of thevelocity by the sign of your answers.)
1 m/s

(b) Determine the velocity of the second log if the lumberjackcomes to rest on it.
2 m/s (a) What is the velocity of the first log justbefore the lumberjack jumps off? (Indicate the direction of thevelocity by the sign of your answers.)
1 m/s

(b) Determine the velocity of the second log if the lumberjackcomes to rest on it.
2 m/s

Explanation / Answer

Mass of of lumberjack ml = 98 kg Mass of log m = 300 kg final velocity of lumberjack = 3.7 m/s a) according to conservation of momentum we have       0= m1 v1 + m v     Therefore              v = - m1 v1 / m                 = - 98 * 3.7 / 300                 = - 1.208 m/s b) for second log         (m1 + m )v =m1v1       Therefore    v = m1 v1 / (m1 +m) = 98 * 3.7/ (98 + 300 ) = 0.911m/s

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