How do I prove that a toy car has constant velocity from timing data?

[totlos]

Homework Statement

Prove that 2 motorized toy cars have a constant velocity.
A car was set up at a marked spot, then turned on and left to go for 3m. This was done three separate times and was timed using 2 timers (2 people).
how can i prove a constant velocity?

I have the averages for both times given and I have averaged out how long it took for the car to go 1m.

What type of graph should I used to prove a constant velocity? How do I prove a constant velocity? Position v. Time or Velocity v. Time graph?

 

[willem2]

you have to measure and graph distance traveled vs. time and see if you get a straight line.

 

[totlos]

Ok, so I got my velocity. So I just graph the velocities on a graph and link them to see if i have a straight line? If the line/velocities are similar can i conclude that they have the same velocities (allowing room for errors, such as reaction time)?