A bullet of mass m = 20 gm is traveling at a velocity of 200 m/s perpendicular t
ID: 2093850 • Letter: A
Question
A bullet of mass m = 20 gm is traveling at a velocity of 200 m/s perpendicular to the long axis of a block of wood resting on a frictionless horizontal surface. The mass of the wood block is M = 10 kg, and its length L = 1m. The bullet bores through the very end of the block, emerging along its original path but with a reduced velocity of 100 m/s
(a) Determine the magnitude of the angular velocity of the block, assuming that the block is thin enough so the moment of intertia about its center of mass is I_cm = (1/12)ML^2
(b) Determine the linear speed of the center of mass of the block.
Explanation / Answer
moment of inertia =ML^2/12
applying law of conservation of angular momentum about the center of mass,
200*20*10^-3=10*(1/12)*w+20*10^-3*100
or w=2.4 rad/s
conserving linear momentum,
20*10^-3*200=10*v+20*10^-3*100
or v=0.2 m/s
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