Aman holding a rock sits on a sled that is sliding across a frozen lake (negligible friction) with a speed of 0.520 m/s. the total mass of the sled, man, and rock is 93.0 kg. the mass of the rock is 0.350 kg and the man can throw it with a speed of 15.5 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).