# Centrifugal Force - continue spinning indefinately in space?

1. Jan 20, 2014

### jocanon

Centrifugal Force -- continue spinning indefinately in space?

I believe it is correct that if you spin up an object in space, like a space ship, it will continue spinning indefinately unless/until another force is applied to stop it from spinning. Then centrifugal force would push the objects in the ship outward and the outer walls of the ship would hold the objects in, simulating gravity. What I don't get is how this system can continue spinning indefinately when the objects inside are putting a force on the walls. Wouldn't that force have the effect of slowing it down over time? It seems odd that this force can exist in perpetuity without any energy source to continue driving it once it is set in motion.

2. Jan 20, 2014

### Decimator

The force on the wall is opposed by the strength of the wall, not by the angular momentum of the centrifuge. It's no different from when you stand on the ground, where the force of gravity is opposed by the dirt you're standing on.

3. Jan 20, 2014

### Bandersnatch

A force has to have at least a component along the direction of motion to change the magnitude of that motion(slow down/speed up). With centripetal force, the force is always acting exactly perpendicular to the instantenous direction of motion, so it can't make anything go faster or slower.

Also, note that forces don't require energy sources. Work requires an energy source, as this is what acts to change the energy of the system on which work is done.

Personally, I blame Star Wars for this 'force=>needs energy' confusion. Since Luke uses the Force during training on Dagobah and is visibly straining, it seems sensible to assume he's using up energy.
If only instead of "The Force" they called it "The Work", or even "The Energy", all would be well.

4. Jan 20, 2014

### pikpobedy

Anything moving inside would tend slow down the rotation of the ship. Recoil from the surfaces is not 100% efficient and heat is generated. Air currents created will impose drag. All irreversible.