# Work and force: frictionless rollercoaster

1. Aug 12, 2012

### yvonne1313

1. The problem statement, all variables and given/known data
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?

2. Relevant 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

3. 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

2. Aug 12, 2012

### yvonne1313

is there enough info, or is there something missing?

3. Aug 12, 2012

### Staff: Mentor

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

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

Last edited by a moderator: May 6, 2017
4. Aug 12, 2012

### yvonne1313

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

5. Aug 12, 2012

### Staff: Mentor

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]

Last edited by a moderator: May 6, 2017