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Unformatted text preview: College Physics I 2011/12 Assignment 3 Suggested solutions 1. A bicyclist of mass 70 kg puts all his weight on each downward-moving pedal as he pedals up a steep road. Take the diameter of circle in which the pedals rotate to be 0.40 m, and determine the magnitude of the maximum torque he exerts. τ max = mgr = mgd /2 = (70)(9.8)(0.4/2) = 1.4 × 10 2 Nm 2. A uniform thin rod of length 2 L and mass M lies horizontally on two smooth supports, as shown in the figure. The two ends of the rod are labeled as A and B . The moment of inertia of the rod about one of its ends is 2 3 4 ML . The gravitational acceleration is labeled as g . If support at A is suddenly removed, at that instant what are (a) the torque about B , (b) the angular acceleration about B , (c) the vertical acceleration of the center of mass, and (d) the vertical reaction force at B ? (a) τ = MgL (b) MgL = I α MgL = (4 ML 2 /3) α α = 3 g /4 L (c) A = L α α = L (3 g /4 L )=3/4 g (d) Mg – R = Ma R = M ( g – 3/4 g ) =...
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This note was uploaded on 02/22/2012 for the course CHEM yscn0027 taught by Professor Drtong during the Fall '10 term at HKU.
- Fall '10