The centripetal force and centrifugal force are the words which are often used in physics and mathematics, applied to the description of rotary motion. Students often confuse these concepts. Sometimes it is difficult for them to find a difference between centripetal and centrifugal force. Nevertheless they cardinally differ from each other.

## Difference between centrifugal and centripetal force

Any object which rotates on a circular trajectory is affected by force. It is directed to the central point of a circle, the described trajectory. Such force is called centripetal.

Centrifugal force is often mentioned as force of inertia or fictitious force. It is generally used for the reference to forces which are connected with the movement in a noninertial reference system.

According to the third law of Newton, each action has opposite to it in the direction and counteraction, equal on force. And in this concept, centrifugal force is reaction to action of centripetal force. Both forces are inertial as arise only at the movement of an object. Also they always appear in couples and counterbalance each other. Therefore in practice they can often be neglected.

## Examples of centrifugal and centripetal force

If to take a stone and to tie to it a rope, and then to begin to rotate a rope over the head, then there will be centripetal force. It will affect through a rope a stone and not to allow it to be removed one distance more than length of the rope as it would occur at a usual throw. Centrifugal force will work exactly the opposite. It will be quantitatively equal and opposite in the direction to centripetal force. Such force of subjects is more, than the massivny body moving on the closed trajectory. It is well-known that the Moon rotates around Earth on a circular orbit. The attraction force which exists between Earth and the Moon is result of action of centripetal force. Centrifugal force, in this case, is virtual and actually does not exist. It follows from the third law of Newton. However, despite abstractness, centrifugal force carries out very important role in interaction of two celestial bodies. Thanks to it Earth and its satellite do not move away and do not approach with each other, and move on stationary orbits. Without centrifugal force they would face long ago.

## Conclusion

1. While centripetal force is directed to the center of a circle, centrifugal is opposite to it. 2. Centrifugal force is often called inertial or fictitious. 3. Centrifugal force is always equal on quantitative value and is opposite in the direction to centripetal force. 5. The word "centripetal" was received from Latin words. "Centrum" means the center, and "petere" means "to look for". The concept "centrifugal" is received from the Latin words "centrum" and "fugere" that means "to run".