Problem: A block of wood having a mass of 05 kg is at rest on a level floor. A lump of putty having a mass of 200 g is thrown at the block so that it is traveling horizontally the instant it hits and sticks to the block. The block and putty slide 1 m along the rough floor. If the coefficient of kinetic friction is 0.2. what was the original speed of the putty?
Strategy: The lump of putty has a totally inelastic collision with the block (it sticks to the block after the collision). Momentum is conserved in this collision since there are no external forces exerted on the system during the collision. Then. the block with putty attached slide on a rough surface and eventually stop. Here we must use the work-energy theorem. since a nonconservative force, Friction, does work on the system and changes its kinetic energy from some initial value to 0. In summary. apply conservation of momentum to the collision. and the work—energy theorem to the sliding portion of the problem. and solve for the original speed of the putty