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A bullet of mass mB = 0.0127 kg is moving with a speed of 105 m/s when it collid

ID: 2144843 • Letter: A

Question

A bullet of mass mB = 0.0127 kg is moving with a speed of 105 m/s when it collides with a rod of mass mR = 6.31 kg and length L = 1.03 m (shown in the figure). The rod is initially at rest, in a vertical position, and pivots about an axis going through its center of mass. The bullet imbeds itself in the rod at a distance L/4 from the pivot point. As a result, the bullet-rod system starts rotating.

a) Find the angular velocity, ?, of the bullet-rod system after the collision. You can neglect the width of the rod and can treat the bullet as a point mass.


b) How much kinetic energy is lost in the collision?

Explanation / Answer

moment of bullet before collision = mvl/4

after collision

mvl/4 = (ml^2/16 + Ml^2/12)w

w = 0.61

energy lost = 1/2mv^2 - 1/2(I1+I2)w^2

= 69.9