Posted by **gary** on Wednesday, April 6, 2011 at 8:30am.

Part A

Each blade on a wind turbine is engineered to produce an effective force through its center of mass that is perpendicular to its long axis. (Part A figure) The magnitude of the force produced by each blade in a wind of speed v is F=(40.0~{\rm kg/s})v. If the center of mass of each blade is r_1 = 11.0 m, what is U_1, the total work done by the wind turbine's blades, in a wind of speed v_1 = 3.90 m/s after 10 revolutions?

Part B

A brake system is tested by rotating a tire and measuring the number of rotations required for the brake system to bring the tire to a stop. (Part B figure) The tire's radius is R_2 = 50.0 cm and the brake system's radius is r_2 = 16.7 cm. A moment of M_1 = 18.3 N \cdot m is applied to the tire for 5 rotations before the brake system is applied. The brake system is composed of two pads that are pushed out against the drum with a force that increases as the tire rotates and is described by F=(10.0\,\theta)~{\rm N}. If the coefficient of kinetic friction between the brake pads and the outer ring of the brake system is mu_1 = 0.550, how many rotations, n, will the tire go through before coming to a stop?