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Time problem involving Mass and a Pulley?

  1. Oct 6, 2007 #1
    1. The problem statement, all variables and given/known data

    Bob and Cathy,two construction workers on the roof of a 20m highbuilding,are about to raise a keg of nails from the ground by means of a light rope which passes over a light and frictinless pulley.

    Bob’s mass= M1=93.1kg
    Cathy’s mass=M2=66.1kg
    The keg’s mass=M3=47.1kg
    The nails mass=M4=64.1kg

    As they cast off the rope, both workers slip off the roof and the following unfortunate sequence of events takes place. Hanging together on the rope Bob and Cathy strike the ground just as the keg hits the pulley. Unnerved by his fall, bob lets go of the rope and watched in stunned amazement as Cathy ascends rapidly until she blips her head on the pulley, But gamely hangs on to the rope. However, when the keg hits bib on the head, the bottom breaks, the nails spill out, and the empty keg now begins a rapid ascent as Cathy returns to the ground. As the keg hits the pulley Cathy is a little stunned as she lies on bob and lets go of the rope only to be hit on the head one last time as the kegs makes its final descent. Ignoring the possibility of mid air collisions, which only ass insult to injury, how long did it take this industrial accident to run its course? Assume that all collisions with the ground or pulley serve to start each subsequent motion from rest so that each trip and down begins with zero velocity.
    Total Time=

    2. Relevant equations
    I cant find the formulas I need for this problem in order to find all 4 times? Please help I've been looking for formulas on this problem for a minute. Thank you Cal

    3. The attempt at a solution
  2. jcsd
  3. Oct 6, 2007 #2


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