# Homework Help: Gravitational Potential

1. Nov 9, 2009

### Joe09

Hi, I did a quick search but didnt find anything relevant so I apologise if this has been covered.

My A2 Physics book says the following:

My question is, the book does not go into any more detail and i am unsure what this equation is ment to actually be. I think it means G but i am unsure.

Appreciate any help.

2. Nov 9, 2009

### tiny-tim

Welcome to PF!

Hi Joe09! Welcome to PF!

There's a slightly confusing difference between potential and potential energy …

electric potential is potential energy per charge, and gravitational potential is potential energy per mass …

that's why they divided Epotential by m.

Gravitational potential (in a uniform gravitational field) is U = gh.

(and btw I think we normally use U rather than V for potential)

3. Nov 10, 2009

### Joe09

Thankyou for the welcome.

Of course how silly of me!

The equation:

Epotential = Etotal - Ekinetic

is equivalent to:

GMm/R = mc2 - 1/2 mv2

So when the physics book divides the equation by m we arrive at:

GM/R = c2 - 1/2 v2

which is equivalent to:

Vgrav = constant - 1/2 v2

I tell ya, working with integrals all day confudles the mind

U? Oh ok, it be nice if the worlds scientists/exam boards/teaching curriculums could agree on a universal symbol. Unless its only the UK which uses V