1. The problem statement, all variables and given/known data Two lumps of clay, each with the same mass 3.5 kg, are sliding on ice, with no friction. One is moving at 4.8 m/s to the right, the other is moving at 2.3 m/s to the left. They collide and stick to one another. Calculate the velocity of the lump of clay after the collision. Is the total kinetic energy constant? 2. Relevant equations (m1+m2)vf=m1v1+m2v2 3. The attempt at a solution Substituted m1 and m2=3.5 kg, v1=-2.3 m/s, and v2=4.8 m/s. With that, I got vf=1.25 m/s. I'm almost sure that one of the velocity is negative since one lump of clay is moving in the opposite direction away from the other. For the second question of whether or not total kinetic energy is constant, I said no.