A classic balsa wood toy airplane is powered by a rubber band that winds up when its four-...

A classic balsa wood toy airplane is powered by a rubber band that winds up when its four-bladed propeller is rotated by hand. When released, the rubber band unwinds and the propeller starts spinning, thus propelling the plane around the room. Model each propeller blade as a slender rod of length L = 6 cm and mass m = 2 g, and neglect air resistance. If we model the rubber band as a linear elastic torsional spring with constant kt = 6 × 10−7 N-m/rad, determine the angular speed of the propeller if it is initially wound up 20 revolutions.

Figure P7.34