a book with a mass of 1.8 kg sits on a bookshelf. if it has a gravitational potential energy of 42 J, how high is the Shelf? The acceleration of the gravity is 9.8 m/s^2. A) 2.1 B) 2.4 C) 1.6 D) 0.9

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.