Question

A man holding a rock sits on a sled that is sliding across a frozen lake (negligible friction) with a speed of 0.540 m/s. The total mass of the sled, man, and rock is 93.5 kg. The mass of the rock is 0.300 kg and the man can throw it with a speed of 15.0 m/s. Both speeds are relative to the ground. Determine the speed of the sled if the man throws the rock forward (i.e. in the direction the sled is moving).