Suppose a 0.250-kg ball is thrown at 15.0 m/s to a motionless person standing on

Question

Suppose a 0.250-kg ball is thrown at 15.0 m/s to a motionless person standing on ice who catches it with an outstretched arm as shown in the figure. (a) Calculate the final linear velocity of the person, given his mass is 70.0 kg.

(b) What is his angular velocity if each arm is 5.00 kg? You may treat his arms as uniform rods (each has a length of 0.900 m) and the rest of his body as a uniform cylinder of radius 0.180 m. Hint: Place the arm rods on top of the body cylinder, i.e., ignore the skater's head. Neglect the effect of the ball on his center of mass so that his center of mass remains in his geometrical center.

Explanation / Answer

a)conserving linear momentum,

0.25*15=(0.25+70)*v

or v=0.05338 m/s

b)conserving angular momentum about the joint,

5*0.9^2/3 * w=0.25*15*0.9

or w=2.5 rad/s

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