# Homework Help: [Solved] Calculating gravitational potential energy

1. Sep 26, 2008

### ultim8

Hi guys. I have this homework question that I've been working on and I cannot even figure out where to start. Here goes:

A 1.80-g particle is released from rest at point A on the inside of a smooth hemispherical bowl of radius R = 25.0 cm (figure below).

Calculate the following:

(a) Its gravitational potential energy at A relative to B.

(b) Its kinetic energy at B.

(c) Its speed at B.

(d) Its potential energy at C relative to B.

(e) Its kinetic energy at C.

So far, I've only been able to calculate (d). I know what I have to do to calculate (a), and I know that (a) and (b) are equal since the bowl is smooth and frictionless.

Here's my problem with (a). I know that PEg=mgy, but I can't figure out how to calculate y. I know it must be something blatantly obvious, but I've been doing physics all day now and I can't even think straight anymore.
I don't need answers; I just need some help figuring out how to get y in (a).

Thanks

EDIT
I just figured out a through d