# Homework Help: Simple question on energies

1. Dec 10, 2011

### bernvall

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

A Particle is place on a smooth sphere of radius b at a distance b/2 above the central plane. As the particle slides down the side of the sphere at what point will it leave?

2. Relevant equations

potential and kinetic energies

3. The attempt at a solution

no idea
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Dec 10, 2011

### Acut

The particle leaves the sphere when the normal force is zero. So the only force acting on it will be the gravitational force.

Find the centripetal component of the gravitational force as a function of the angle theta. Then write the expressions for the conservation of mechanical energy, and use the fact that F = (mv^2)/b. A few mathematical manipulations later, you will find an expression of the type sin θ = constant, or cos θ = constant. Use the arc sine or arc cosine functions accordingly to find θ. That will be your answer. You may transform to rectangular coordinates if the problem asks for it.

I know it sounds like a lot of work, but it actually isn't.

3. Dec 11, 2011

### bernvall

Thanks, i actually managed it, it came b/3 :)

Thanks for the help.