Which of the following leads to the conclusion that momentum is conserved? . a) proportionality between weight and mass. b)equal magnitude and opposite direction of action-reaction pairs of forces. c) equivalence principle. d) relation between translation and rotation of an object that is rolling.

Awind turbine is rotating counterclockwise at 0.5 rev/s and slows to a stop in 10 s. its blades are 20 m in length. (a) what is the angular acceleration of the turbine? (b) what is the centripetal acceleration of the tip of the blades at t=0s? (c) what is the magnitude and direction of the total linear acceleration of the tip of the blades at t=0s?