Physics behind roller coasters !

For many people, there is only one reason to go to an amusement park: the roller coaster. Some people call it the "scream machine," with good reason. The history of this ride reflects a constant search for greater and more death-defying thrills.

How does a roller coaster work?
What you may not realize as you're cruising down the track at 90 km/h is that the coaster has no engine. The car is pulled to the top of the first hill at the beginning of the ride, but after that the coaster must complete the ride on its own. You aren't being propelled around the track by a motor or pulled by a hitch. The conversion of potential energy to kinetic energy is what drives the roller coaster, and all of the kinetic energy you need for the ride is present once the coaster descends the first hill. Once you're underway, different types of wheels help keep the ride smooth. Running wheels guide the coaster on the track. Friction wheels control lateral motion (movement to either side of the track). A final set of wheels keeps the coaster on the track even if it's inverted. Compressed air brakes stop the car as the ride ends.

The types of roller coasters
Roller coasters can be wooden or steel, and can be looping or non-looping. You'll notice a big difference in the ride depending on the type of material used. In general, wooden coasters are non-looping. They're also not as tall and not as fast, and they don't feature very steep hills or as long a track as steel ones do. Wooden coasters do offer one advantage over steel coasters, assuming you're looking for palm-sweating thrills: they sway a lot more. Tubular steel coasters allow more looping, higher and steeper hills, greater drops and rolls, and faster speeds.

My favourite roller coaster
My favourite roller coaster has got to be Millenium Force at Cedar Point in Ohio, United States.When I visited this amusement park 2 years ago, I was thrilled to go on this ride. Although its height had been surpassed by Top Thrill Dragster, opened in 2003, I have never experienced the thrill I encountered on Millenium Force. This immense ride has a height of 94 metres a length of 2,010 metres with a maximum speed of 150 km/h.

RESOURCES
http://themeparks.about.com/gi/o.htm?zi=1/XJ&zTi=1&sdn=themeparks&cdn=travel&tm=108&gps=343_533_1345_600&f=20&su=p974.8.121.ip_p284.9.336.ip_p531.51.336.ip_&tt=2&bt=1&bts=1&zu=http%3A//cec.chebucto.org/Co-Phys.html

http://tlc.howstuffworks.com/family/roller-coaster3.htm

http://www.physicsclassroom.com/mmedia/circmot/rcd.cfm