A baseball pitcher takes 5 seconds to pitch a ball. While pitching the pitcher?s

Question

A baseball pitcher takes 5 seconds to pitch a ball. While pitching the pitcher?s upper arm rotates through an angle of 40 degree and the lower arm rotates through an angle of 80. The distance from the shoulder joint to the elbow is 35cm and the distance from the elbow to the baseball player?s hand is 47 cm The pitcher s shoulder joint (point C) does not have any translational velocity. The upper and lower arms, the hands and baseball travel in the same x-y plane and the axes of rotation of the shoulder and elbow joints are in the z-direction. (z-axis is coming out of the page) a) Find the angular velocity and angular acceleration of upper arm (point B) at the instant the pitcher releases the ball. b) Find the velocity of the upper arm at point B the instant the pitcher releases the ball. c) Find the acceleration of the upper arm at point B the instant the pitcher releases the ball. d) Find the velocity of the pitcher?s hind at the instant the ball is released if the pitcher?s lower arm is parallel to the y-axis when the ball is released.

Explanation / Answer

a) ? = (?)/t

  ? = 40pi/180

= 0.698 rad

? = 0.698/5 = 0.1396 rad/sec

  ? = ?/t = 0.1396/5 =0.0279rad/s2

b) v = r?

= 0.35 (0.1396)

= 0.0489m/s2

c) a = r?

= (0.35)(0.0279)

= 9.765x10-3m/s2

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