"In Section 1.3, you will consider the gravitational potential, kinetic, and the total mechanical energy of a cart moving down an inclined ramp in a cart-Earth system. (Refer toFigure 6. 2). Define the gravitational potential energy to be zero when the cart is at the bottom of the ramp. Write an expression for the gravitational potential energy of the cart-Earth system in terms of the cart’s mass mm, the cart’s position along the inclined ramp xx, and the angle of the ramp T. "

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero.