Here are some fun online applications that you can use to make roller coasters and learn a little about physics along the way. Students will choose track heights, shapes, and dips to create the ultimate thrill ride that is not too scary or dangerous.
Caret's Roller Coaster Designer:
Fossweb's Roller Coaster:
Spark Lab's Roller Coaster Designer:
Roller Coaster Creator:
If you want a great lesson plan involving roller coaster physics, take a look at Amusement Park Physics and Take a Roller Coaster Ride.