I'm sure this is elementary for this forum, but can someone help me figure out if my son's science fair project results are correct? He rolled his toy car, with and without weight added, down hill and measured the time to get to the bottom of the hill and the distance traveled once the car hit the flat part of the track. He kept bumping into the track and messing it up so I'm not sure if his results are accurate. He has both cars traveling down hill in the same amount of time and the heavier car traveling farther. Does that sound right? How would you explain it in elementary age terms? Thank you in advance.