Potential energy of a particle along x-axis varies as shown in the figure. If the particle is released from rest at a point on x-axis.

F=-dUdx if slope is +Ve body will move in the negative X direction. Also, since the slope is constant acceleration is constant. Thus dvdt= constant and as a result dvdxdxdt = constant.dvdxV = constant. On integrating, V22= X + C. Thus V2 is ∝X.