# Work and force: frictionless rollercoaster

## Homework Statement

A frictionless rollercoaster does a vertical loop with a radius of 6.0m.
a) what is the minimum speed that the roller coaster must have at the top of the loop so that it stays in touch with the rail?

## Homework Equations

2∏r should be used for the circumference but i dont know which equation of motion to use, v=u+gt/ v=u+at

## The Attempt at a Solution

i worked out the circumference to be 37,70m but im stuck with that and dont know what to do next

## Answers and Replies

is there enough info, or is there something missing?

NascentOxygen
Staff Emeritus
Science Advisor
Hi yvonne1313! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

For circular motion: what equation do you know involving centripetal acceleration?

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i only know the energy conservation approach, i think thats what its called, with the equations of motion, w=f.s, ep=mgh, ek=0.5mv^2

NascentOxygen
Staff Emeritus
Science Advisor
It sounds like you might have missed the lessons on circular motion.

So you'll have to self-study that chapter in your textbook, or now that I've told you some terms to look for, try the web alternative: http://img811.imageshack.us/img811/5412/thgooglefriend1.gif [Broken]

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