Two blocks are hung by a string draped over a pulley, a 1.3-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. Required:
a. What is the change in the gravitational potential energy of the system of blocks and Earth when the 2.9-kg block has dropped 0.61 m?
b. What is the change in the kinetic energy of the system between release and this instant?
c. What is the velocity of the 1.3-kg block at this instant?

(a) assume the equation x = at^3 + bt describes the motion of a particular object, with x having the dimension of length and t having the dimension of time. determine the dimensions of the constants a and b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.) (b) determine the dimensions of the derivative dx/dt = 3at^2 + b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.)