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A bullet with a mass m = 4:83 g and initial speed of 330 m/s passes through a wh

ID: 2090582 • Letter: A

Question

A bullet with a mass m = 4:83 g and initial speed of 330 m/s passes through a wheel which is initially at rest as in the gure. The wheel is a solid disk with mass M = 2:29 kg and radius R = 18:6 cm. The wheel rotates freely about an axis through its center and out of the plane shown in the gure. The bullet passes through the wheel at a perpendicular distance 14.8 cm from the center. After passing through the wheel it has a speed of 249 m/s.


(a) What is the angular speed (rad/s) of the wheel just after the bullet leaves it?

(b) How much kinetic energy (J) was lost in the collision?

The correct answers are (a) 1.46 rad/s and (b) 113 J

I know how to calculate the angular speed for part (a) I just can't understand how to calculate part (b)

Explanation / Answer

Initial Energy = 0.5*m*330^2 ;

Final Energy = 0.5*m*249^2

Energy Lost = Initial - Final = 113.6 J