a cart is constrained to move along a straight line. a varying net force along the direction of motion is exerted on the cart. the cart’s velocity v as a function of time t is shown in the graph above. the five labeled points divide the graph into four sections.

During cooling, the kinetic energy of the molecules falls. why does this happen? a.the motion of the molecules increases. b. the motion of the molecules slows down. c.the van der waals forces between molecules decrease d. the forces of attraction between the molecules are overcome.