# Inertia in circular motion

1. Oct 2, 2004

### darknum

is there a way to keep inertia in circular motin?

2. Oct 2, 2004

### Tide

Are you thinking of angular momentum?

3. Oct 2, 2004

### arildno

You will always need a net centripetal force (acting radially inwards) on an object to have it moving in a circular orbit, if that was what you were after.

4. Oct 4, 2004

### spacetime

A body in circular motion will remain in circular motion if no unbalanced forces act on it. Is it the truth of this statement that you are trying to ask about?

If yes, then the answer is NO. First of all, a body can be in circular motion only if a net force acts on it. And to continue with that circular motion, a force is continually required.

Another interesting point is that the earth continues rotating even when no force ( to cause rotation ) acts on it. This is because earth is an ensemble of particles and those particles are in continuous circular motion due to forces by other particles. If you take them as a whole, which is the earth, then it needs an external force to keep it moving in a circle.

spacetime
www.geocities.com/physics_all/index.html

5. Oct 8, 2004

### roger

DEAR SPACETIME,

WHAT FORCE CAUSES THE EARTH TO CONTINUE ROTATION THEN ?

AND HOW DO YOU KNOW THAT THE CONSTITUENT PARTICLES ARE IN CIRCULAR MOTION ?

<> ROGER <>

6. Oct 9, 2004

### spacetime

Earth's rotation

Earth's rotation doesn't require an external force. It is the circular motion of the constituent particles that does. Earth's rotation is a result of all those motions combined.

And where do those particles get the force from? They get it from each other. We are considering only the circular motion of the particles.

spacetime
www.geocities.com/physics_all