What is a fictional force in physics

Centrifugal force an apparent force - centrifugal force and centripetal force

The centrifugal force as an apparent force

Centrifugal force

What is the centrifugal force?

The Centrifugal force or Centrifugal force is a Sham power, in the accelerated frames of reference occurs. But what is one Sham power and how is it created? To understand this, let's look at a simple example that I'm sure you know: a carousel.

We consider a carousel with the radius $ r $ dealing with the Angular velocity $ \ omega $ rotates. So when you're sitting on the very edge, you're moving with the Track speed $ v = \ omega \ cdot r $ on a circular path. At every point on the circular path, the orbital velocity is always at a $ 90 $ ° angle on the radius $ r $, i.e. it lies tangential at the circular path. After this first Newton's law (A body moving in a straight line at constant speed remains in the state of straight movement as long as no forces act on it.) your body actually wants to follow this straight-line movement, i.e. keep flying straight ahead. It's because of his inertia, which is why you also get one Inertial force speaks. You feel this effect in a carousel - it feels like you are being pulled outward. The centrifugal force can be calculated with a formula:

$ F_z = \ frac {mv ^ {2}} {r} = m \ omega ^ {2} r $

However, there is no actual physical force at work here. The impression only arises because your body is prevented from following a straight line movement. Therefore one speaks of an apparent force when talking about centrifugal force. It only occurs within the rotating carousel, i.e. within the accelerated reference system.

centripetal force

Your body is blocked from your seat from flying straight ahead. So the seat exerts a force that forces you on a circular path - against yours Inertial resistance. This force is called centripetal force.

It has to be exactly opposite to the centrifugal force, because you stay on the circular path. Therefore, the formula also applies here:

$ F_z = \ frac {mv ^ {2}} {r} = m \ omega ^ {2} r $

In contrast to centrifugal force, centripetal force is one real Force, that is, it works independently of the frame of reference. The physical cause for this force can be of different nature, so it is a Deputy. In the case of the carousel, it is mechanical forces that force you onto the circular path. In the case of the earth orbiting the sun, it is gravitation. In the case of charges on circular paths, it is the Lorentz force and in the case of a car that turns sharply into a curve, it is the friction between the tires and the asphalt.


Let us summarize once again the most important points and differences between centrifugal force and centripetal force. The centrifugal force is an apparent force that only works in an accelerated system. It is called pseudo-force because it only results from the inertia of a body and no physical force is at work.

The centripetal force is one real Force that can have different physical causes. It forces a body on a circular path and can be observed independently of the reference system.

By the way: In our example we are using one closed However, circular orbit, centrifugal and centripetal forces also occur when no closed circle is traversed. For example, you also feel a centrifugal force when you drive your car through curves.

This video

In this video you will learn the basics of centrifugal and centripetal force. You also learn how to calculate centrifugal force. In addition to video and text, you will find exercises and a worksheet on this topic.