A Suburban that weighs 6500 lbs moving at 40 mph runs into a Smart Car that weighs 1500 lbs that is moving at 15 mph. The two vehicles stick together, how fast
are they moving after the collision?

Ithink it’s cancer risk

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. 

It would stay the same