Solve the all parts of given problem:
Problem: Two blocks are hung by a string draped over a pulley, a 1.5-kg block on the left and a 3.0-kg block on the right. The two blocks start out at rest and at the same height.
Part I: What is the change in the gravitational potential energy of the system of block and Earth when the 3.0-kg block has dropped 0.50 m?
Part II: What is the change in the kinetic energy of the system between release and this instant?
Part III: What is the velocity of the 1.5-kg block at this instant?
I need help to find the change in the kinetic energy of the system between release and this instant.