Find a paper towel roll or wrapping paper roll. If you have hot wheels tracks you could use them as well.
Set it up the roll on an incline like pillow, chair or couch.
Attached 4 or 5 pieces of paper together and make a number line from 1-10 evenly spacing out numbers. Place the number line at the end of the track or paper towel roll.
Take turns pushing the car down the track and see how far your car goes before it veers off track. How far did your car go? How much farther did it go the next time?