- #1
jakec
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Homework Statement
To lower himself from a balcony an 80kg stuntman grabs a rope connected to a 400kg cylinder with a 1.2m diameter that is free to rotate about its axis of symmetry. What is the stuntman's acceleration as he falls?
Homework Equations
I missed this on a homework assignment. I know the correct answer is 2.86m/s2 but I can't find what I did wrong.
The Attempt at a Solution
moment of inertia for a cylinder: I=1/2 Mr2
radius of cylinder = 0.6m
torque applied by stuntman = mgr = 80kg * 9.8m/s2 * 0.6m = 470.4Nm
Using t = Iα
470.4Nm = (0.5 * 400kg * 0.6m2)α
α = 470.4Nm / (0.5 * 400kg * 0.6m2) = 6.53rad/s2
a = αr = 6.53rad/s2 * 0.6m = 3.92m/s2
What am I missing?