# A 215 g particle is released from rest at point A (the middle of one side) inside a smooth hemispherical bowl of radium 30.0 cm. Calculate the gravitational potential energy at A relative to B. (B is in bottom-middle of the bowl)

Ok, so PE_g=mgh. How would I find the height of A? If necessary, I could scan the diagram shown in the book.

PS I'm still stuck on my other question if you have time :)

What is the radius? It is a hemisphere.

ok, I made a similar image on paint

img71.imageshack.us/ img71/1637/mathga5.png

now, the distance from A to B is not the same as the radius, right?

Lol

## Ok, y'all. This is the moment you've been waiting for. All these years, fate has brought me here. I come with...The answer!

So, you're gonna want to use the Gravitational Potential Energy equation, which is mgh. Using what the word problem gives us, we know (additional to gravity):
m=mass=215g
g=gravity=9.8m/s^2
h=height, which in this case is derived from the radius, which is 30cm
(This would be the height because if you think about it it is the length from the opening of the bowl to the bottom, just in the case of it being radius it is true in all directions, and based on the picture (at least provided in my textbook) it confirms the accuracy of using the radius rather than finding diameter- idk if this made sense but Ima hope so XP.)
Now, my teacher gives us the answers, so based on the answer being 0.6333 Joules (J) I discovered that the key is *converting*.
So, by converting the mass 215g into kg, which is 1g=0.001kg, gives you m=0.215kg
And by converting height, 30cm, into m, which is 1cm=0.01m, gives you
h=0.3m
When these new values are plugged into the equation, mgh, you get (0.215)(9.8)(0.3)= 0.632 J, which just about rounds to 0.633. It all depends on how you round through the process of getting your answer. Don't forget your units though!
I hope this made sense and I didn't just lead you astray!