Physics Homework

This is what happens when I get a bad professor. I took physics last fall, and the prof had a distinct "if you're not able to teach it to yourself, there's nothing I should have to do about it" style, which... sincerely frustrated most if not all of his students.

If a 100g car is placed on a wooden ramp 2 feet long by 21cm high and attached to a level track another 2 feet long, and let go, at what time will the car reach the end of the track?

NEVER YOU BLOIT, an elephant appeared out of nowhere and SAT on the track!

At this point I would fume and stomp away.