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

Question

A lumberjack (mass = 98 kg) is standing at rest on one end of a floating log (mass = 290 kg) that is also at rest. The lumberjack runs to the other end of the log, attaining a velocity of +3.2 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.

(a) What is the velocity of the first log just before the lumberjack jumps off? (Indicate the direction of the velocity by the sign of your answers.) m/s

(b) Determine the velocity of the second log if the lumberjack comes to rest on it.

Explanation / Answer

Mass of of lumberjack ml = 98 kg

Mass of log m = 290 kg

final velocity of lumberjack = 3.2 m/s

a) according to conservation of momentum we have

0= m1 v1 + m v

Therefore

v = - m1 v1 / m

= - 98 * 3.2 / 290

= - 1.081m/s

b) for second log

(m1 + m )v =m1v1

Therefore

v = m1 v1 / (m1 +m)

= 98 * 3.2/ (98 + 290 )

= 0.8082m/s

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.