# Earth Gravitation problem

1. Jan 25, 2010

### mkbh_10

We know that N = mg , where N is normal reaction and mg is the force with which earth is pulling a body . Now if i place another body ,lets say 10 ^12 kgs at a distance of 1 m from the body , will the larger body pull the smaller body horizontally towards itself , both these bodies are in contact with the surface of earth , not joined to surface. will friction come into play in opposing the attraction towards each other ??

Now the problem i am facing is that when the larger body rests on the surface, it automatically becomes part of (earth+body) which is a composite system and 10^12 < < 10^24(mass of earth ) so the smaller body wont experience any pull unless the mass becomes comparable to the order of earth's mass and if we have a very dense body , 10^12 kg packed in a meter then it will pull the smaller body with a force of 6.7 m/s^2 which is comparable to 9.8 of earth .

Also it must be that for the larger body to pull smaller one it shud have mass much greater than earth to overcome earths gravity

Last edited: Jan 25, 2010
2. Jan 25, 2010

### banerjeerupak

As soon as you put another large mass into the system, you have to consider the shifting of the centre of mass. The earth will exert a pull on this body and this body will exert a force of attraction on the earth. The centre of mass will shift according to the mass of this new body in space and the mass of the earth. so the small mass will shift towards the common centre of mass.