# Box on a sphere is nudged- when does it fall off?

1. Feb 22, 2012

### Aesops

Box on a sphere is nudged-- when does it fall off?

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

A box of mass "m" is placed on a sphere of radius "r". The box is given an extremely small nudge to get it moving.

(a) What is the maximum speed the ball may have without leaving the sphere?
(b) At what angle from the vertical does the ball last touch the sphere?

2. Relevant equations

I think this is a question requiring energy, so

Ugpe = mgh
KE = mv2/2

But knowing there is a circle involved,

Fc = mv2/r

3. The attempt at a solution

I'm not sure how to attack the problem... I do know that our physics class has not yet gone over anything beyond Newton's three laws and the concepts of gravitational potential and kinetic energy.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 23, 2012

### kushan

Re: Box on a sphere is nudged-- when does it fall off?

ball on sphere?

3. Feb 23, 2012

### Staff: Mentor

Re: Box on a sphere is nudged-- when does it fall off?

That's all you need. Hint: In addition to energy conservation, make use of Newton's 2nd law. What forces act on the box as it slides down?