# A question on gravity

1. Aug 21, 2009

### Learnphysics

Well, i know i might be far oversimplifying this as its not understood properly by science yet but.

A permanent magnet seems to lose its magnetism slowly as it does work on other objects. (conservation of energy)

Is this in any way true for gravity, does a mass "lose" its pulling power after doing sufficient work. (of course we've never observed this happening).

And if this DOESN'T happen, isn't gravitational "pulling" is essentially infinite? sure you have to put in kinetic energy to increase the Gravitational potential energy, (the object has to start at a distance AWAY from the gravity-causing-mass) but other then that, can the pulling power of gravity be described as infinite, only dependent on the existence of another object with which to exert itself?

2. Aug 21, 2009

### fatra2

Hi there,

You seem to be mixing up things, like primary forces and conservation of energy. Magnetism decreases in a magnet due to the alingment of its atoms/molecules. If you rearrange them in their original position, you will increase the magnetic field.

Gravity, like the other three primary forces, does not fade with time.

You are absolutely right to say that gravity's action is infinite, but it decreases by the square of the distance between two objects. Therefore, very far away objects have pratically no more effect on us (this is where we say that it becomes negligeable).

Cheers

3. Aug 21, 2009

### gmax137

No no no! This is not right. Conservation of energy does not mean that the magnet's force somehow gets "used up." What it does mean is that the changes in position (distance from the magnet) and velocity of the "other object" can be tracked as trading off potential energy for kinetic energy.