# Can i understand gravity better?

1. Sep 4, 2011

### Jpjangz

hi, i have 2 question sorry
And sorry to write a huge chunk of these things making your eyes all tired out

First, so is the G 6.67 x 10 to the power of negative 11 is the universe G? Or just applies to earth itself only.
Moreover, am i right to say that all gravity is affected by the mass and the radius of the star or planet itself?

Second, so lets imagine two scenarios

1) Planet A approaching earth having same mass, but smaller in size meaning shorter diameter than earth, does it mean that earth will accelerate towards it?

2) Planet B approaching earth having mass greater than earth, but same now same size meaning in same diameter, does it mean that earth will also accelerate towards it?

Or, is the great gravity provided by the sun that caused our earth to not move towards these two planets because the king planet attractor in some sense make these gravity forces from planet A and B somewhat useless.

Sorry wrote a chunk of these things

2. Sep 4, 2011

### Staff: Mentor

It's a universal constant describing the gravitational attraction between all masses.
The mass, yes; the radius, no. The gravitational force between two masses depends only on their mass and the distance between them.

The gravitational attraction does not depend on the size of the planet, only its mass (and its distance from the earth).

The resulting acceleration depends on all the forces acting on a body.

3. Sep 4, 2011

### Jpjangz

Sorry, hands itchy, thus, so is it that when a two planets get close enough to each other with a set of mathematical formula, then they will we somehow collide or attract?

And the force you mean; is it the acceleration and the mass of it somewhat the formula F=MA which contributes much to this scenario? Then so, is momentum part of this phenomenon too?

Sorry~ just curious very curious ahh~