This year when you go to the amusement park bring a cam corder and a camera. Video tape the roller coaster rides. Choose a hill where the cars are not moving too fast. Zoom the cam corder on the hill without moving the cam corder. The train will pass in and out of view. Next year show the class the video tape. Have the students use the tape to calculate the velocity of the train at this spot on the hill. It is great real life practice. Below is an example of the view frame for such a taping.

With the camera, take pictures of loops, hills, curves, etc. Either use slide film or make these pictures into overheads. You can show them to the students before they go so they will be prepared to take the right measurements. You can also use these pictures so students can look at the hills on a roller coaster and rate them in terms of velocity over the top of each.