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# Daily Archives: April 15, 2012

## Doubt in Law of Gravitation

According to law of gravitation
F=g*(m1*m2)/r^2
If we bring two objects close to each other say our hands then the distance will be zero and the force of attraction will become infinite because r will we zero. Therefore F will become infinite but this is not the case.
When we touch our both palms together we can easily pull then away.

When we consider the distance, it is between the center of mass of the two bodies under consideration. When we bring our hands together the distance between their CM is not zero.

Other wise, the two particles under consideration must be point masses.

Then if you consider two atoms or two nuclei, the forces that come into play will be different if we decrease the distance between two atoms or nuclei. The attraction will turn into strong repulsion when the limits are exceeded.

## What is gravity?

So I’ve been thinking about what gravity really is, I know it’s a rather weak force, but dominates the universe.  Is there a possibilities that gravity is actually inter-molecular forces?

## Direction of velocity and acceleration

Is it possible that the velocity and the acceleration of a body point in opposite directions? if yes then why?
if no then why?

Yes. It is possible for the direction of acceleration to be opposite to the direction of velocity.

Acceleration is the rate of change of velocity. If velocity is increasing while moving in a straight line then the direction of acceleration is same as the direction of velocity.

It the velocity is decreasing whil travelling in a straight line then the direction of acceleration is opposite to the direction of velocity.

Example: When a stone is thrown vertically upwardsm its acceleration is downwards and velocity is upwards.

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