Centifugal force

1. Feb 28, 2006

Wiz

hi,
we all know tht when a body moves in a circular path,it experiences an outward force(eg:a coin on rotating disc gets thrown outward).Theoritically fine.But can anyone give me the LOGICAL explanation for this?Wht does it get thrown outward?

Also consider a person in a rotar standing with back touched to its wall...when the rotar starts rotating and the floor is moved down,the person does not fall since his weight is balanced by the frictional force which depends on the normal force.Which means that the person is exerting a force on the wall of the rotar..if centrifugal force is fictious then which force is this?..I am so deeply confused..
wiz

2. Feb 28, 2006

Staff: Mentor

A force is required to change the direction of an object (make it move in a circular path). That's the force that is felt.

3. Feb 28, 2006

Eivind

There is no such thing as centrifugal force, its rather the lack of force that is felt.

4. Feb 28, 2006

Staff: Mentor

What you actually feel, as Russ indicated, is the centripetal force that keeps you moving in a circle. In the rotor example, you feel the wall pushing against you--centripetal force. All this is perfectly understandable when viewed from the usual inertial frame; Newton's laws demand it.

The coin on the rotating disk is equally understandable: To keep the coin in place on the rotating disk requires a certain centripetal force; if the friction is insufficient, then the coin will tend to slide along its direction of motion. Inertia (Newton's 1st law) in action.

The so-called "fictitious" forces arise when one views things from a non-inertial, accelerating frame. In such a frame, Newton's law's don't apply without modification. The modification needed is the addition of inertial forces. In the rotor example, the wall exerts a "real" force against you ("real" just means that there is a real agent producing the force: the wall). To apply Newton's laws from the view of the rotating frame you must include the centrifugal force acting outwards: coupled with the force of the wall, the net force is zero.

But Eivind is correct that centrifugal force doesn't exist as a real force, it is only an artifact of using a noninertial frame of reference. But the effects are quite real.