# Gravitational constant?

1. Apr 2, 2010

### GreatEscapist

In my physics class, we learned that everything accelerates towards each other at 6.67 x 10-11. I'm not sure what about that doesn't make sense (We didn't talk about it much, but we're expected to know about it) but something doesn't. How can EVERYTHING accelerate at the gravity? Uhhh, wouldn't a bigger mass go faster? Earth goes 9.8 m/s2, so where does G come in to play?
And how the crap did someone figure that out, anyway?

2. Apr 2, 2010

### Staff: Mentor

That's the gravitational constant G (in m3 kg-1 s-2), not the acceleration of anything.

3. Apr 2, 2010

### bp_psy

This is incorrect. To find the force between 2 objects with respect to each other we use the following formula $$\ F=G \frac{m1*m2}{r^2}$$. Where m1 and m2 represent the mass of the objects and r is the distance between them.G is your gravitational constant which is not an acceleration . To find the acceleration on one of the objects at a certain distance from the other you take its mass out of the formula. The acceleration of object 2 at distance r from object 1 is $$\ a=G \frac{m1}{r^2}$$ directed from 2 to 1

Last edited: Apr 2, 2010
4. Apr 2, 2010

### TurtleMeister

You may also be confusing little g with big G. The 9.8 m/s2 that you referred to is little g, and it is an acceleration. It is the acceleration that all objects fall at surface of the earth. Big G is as the previous posters described. You may find this page helpful: http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html

5. Apr 2, 2010

### GreatEscapist

Oh.
This would explain why my homework always comes out wrong.

6. Apr 2, 2010

### cragar

G was measured by Henry Cavendish using a torsion setup , google it to get more precise details.