Flicking bottle caps is probably something you have some experience with. It involves rapid flexion of the proximal interphalangeal (PIP) joint of the middle finger while the distal phalangeal joint stays fixed in full extension. A skilled flicker can impart a linear velocity of 5 m/sec on the bottle cap. The flick starts from rest and is completed at 90 degrees. During the flick, the center of the bottle cap is a distance of 4 cm from the PIP joint.
a. What is the angular velocity of the PIP joint just as the cap is flicked?
b. If the flick is completed in 0.05seconds, what is the average angular acceleration?