Work and force: frictionless rollercoaster

[yvonne1313]

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 don't 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 I am stuck with that and don't know what to do next

 

[yvonne1313]

is there enough info, or is there something missing?

 

[NascentOxygen]

Hi yvonne1313! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

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

 

[yvonne1313]

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

 

[NascentOxygen]

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