Imagine a book that is falling from a shelf. At a particular moment during its fall, the book has a kinetic energy of 25 J.
What was the initial potential energy of the book, and what is its total kinetic energy at the instant just before it strikes the floor?

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.