A lumberjack (mass = 98 kg) is standing at rest on one end of afloating log (mas

Question

A lumberjack (mass = 98 kg) is standing at rest on one end of afloating log (mass = 215 kg)that is also at rest. The lumberjack runs to the other end of thelog, attaining a velocity of +3.5 m/s relative to theshore, and then hops onto an identical floating log that isinitially at rest. Neglect any friction and resistance between thelogs and the water. (a) What is the velocity of the first log just before thelumberjack jumps off? (Indicate the direction of the velocity bythe sign of your answers.)
m/s

(b) Determine the velocity of the second log if the lumberjackcomes to rest on it.
m/s (a) What is the velocity of the first log just before thelumberjack jumps off? (Indicate the direction of the velocity bythe sign of your answers.)
m/s

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

Explanation / Answer

Mass of of lumberjack ml = 98 kg Mass of log m = 215 kg final velocity of lumberjack = 3.5 m/s a) according to conservation of momentum we have       0= m1 v1 + m v     Therefore              v = - m1 v1 / m                 = - 98 * 3.5 / 215                 = - 1.595 m/s b) for second log         (m1 + m )v =m1v1       Therefore    v = m1 v1 / (m1 +m) = 98 * 3.5/ (98 + 215 ) = 1.0958m/s

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