What is centripetal and centrifugal force

Circular motion

Let us describe the circular motion of a body from Laboratory system (i.e. we consider the circular motion from the outside), we have to assume a centripetal force on the body. If this force directed towards the center of the circular motion were not present, the body would fly away in the tangent direction according to the law of inertia.

The viewer, who has not yet dealt very intensively with the circular movement, will first speak of the outward centrifugal force when asked about the forces during the circular movement, which he has already felt himself when cornering. This is correct for an observer who is in an accelerated (rotating) frame of reference and everything he observes and measures in it relates to this system. The driver is in the cornering accelerated frame of reference Automobile.

Imagine a little man sitting on a uniformly circling ball. It feels that a centripetal force pulls towards the center and acts on the bottom of the trousers to execute the circular movement. If this force were not there, another force of centrifugal force (Latin: fuga = flight) would pull the male down outwards from the ball. Centrifugal force and centripetal force create a balance of forces for the male that enables him to sit quietly on the ball. As the angular speed increases or the distance from the center increases, the male feels a growing centrifugal force, which must be compensated for by holding on to the surface more firmly.


Note: Needed to describe the uniform circular motion

the observer in the laboratory system
only the centripetal force
the observer in the rotating system
the centripetal force and the centrifugal force

The main difference between the accelerated and non-accelerated reference system:

The centrifugal force is a force that opposes the acceleration of the reference system. They are known as Inertial force, it is to be measured directly in the accelerated system. Such inertial forces are often also called Pseudo-forcesbecause they are not recognizable in the non-accelerated system.

However, the accelerated reference system has the problem that Newton's laws no longer apply without restrictions: Newton's 3rd law says that for every force on one body, there must be a counterforce on another body. This is not fulfilled for pseudo-forces, they have no "reaction". The uniform, rectilinear movement of a body in equilibrium of forces is also not given in an accelerated reference system.

In non-accelerated frames, however, all Newton's laws apply. Such systems are called Inertial systems. (Latin inertia = inertia)

A traveler sitting in an approaching train observes that the station is accelerating in the horizontal direction, although there is no force acting on the station in the horizontal direction and a bird flying uniformly across the direction of the path is flying through a curved path. The law of inertia does not apply in the accelerated frame of reference, but it does in the inertial frame.

Technical applications in which centrifugal force is used are, for example, centrifuges.