See what's waiting in the wings and vote for what you would like to see next. This program demonstrates moving graphics by letting you drop a ball and watching it bounce. That seems pretty impressive to me. First a little physics - gravity makes everything speed up at the same rate.
Pixels replace feet and loops replace seconds.
We'll treat each time through the loop as one time interval. So the first thing we have to do when the user presses the start button is begin changing the top property of our ball by V pixels each time through the loop. 1 the second time, etc. Besides changing the velocity, the loop must also detect when the ball hits the floor and reverse direction. You can scope that out from the code.