8. a train rolls at a constant speed of 10 m/s across a horizontal track. a child standing on the flatbed of the
train throws a ball so that it appears to move straight up to an observer standing next to the track.
a. what is the horizontal speed of the ball relative to the observer?
b. what is the horizontal speed of the ball relative to the train?
c. if the ball is also thrown upward with a speed of 20 m/s, what is the overall initial speed of the ball
relative to the train?

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.