Centrifugal force is an apparent force that every body is subjected to when it rotates and causes an outward displacement. Something that a priori may be somewhat complicated to understand, but that we will explain better if we offer you its formula, we see how it is applied and also some examples of centrifugal force.
What is centrifugal force and how does it work: formula and examples
The first thing we would have to explain to understand well what centrifugal force is, is that it as such does not exist or is not a force itself. A force constitutes a mechanical action suffered by an object, such as mass, for example. This type of force is represented by a vector that has a point of application , a direction, a direction and an intensity expressed in Newtons (N). Centrifugal “force” is just a misnomer, because it is just an effect observed in the presence of another force, which we will quote later (centripetal force).
Centrifugal force (tending to move away from the center) is just a fictitious force, or inertial force that can be observed when studying the motion of a non-Galilean frame of reference, that is, when an object is in motion and is subjected to forces (that is, the opposite of a Galilean frame of reference, which is an isolated object, which follows linear motion and is not subject to any force).
It only exists through the execution of the centripetal force (→ which tends to get closer to the center), which is the so-called “real” force that is exerted on an object to impose a circular, therefore non-linear path on it. For example, a ball attached to a rope that rotates thanks to the movement of our hand suffers centripetal force.
The centrifugal force and the centripetal force are opposite , the centripetal force, being perpendicular to the trajectory, is directed towards the center of rotation, while the «centrifugal force», also pependicular to the axis of rotation, is directed towards the center of rotation outside the circle.
We can thus summarize that the centrifugal force is an apparent force that is observed in non-inertial systems in rotary motion (of any type)
In the case of a plane system , in uniform rotational motion with constant angular velocity, we can write a simple formula for the centrifugal force that allows us to calculate the force that appears to the integral observer.
F_ {cf} = m omega ^ 2r
where m is the mass of the body and r the position of the body with respect to the origin O ‘= O.
Relationship between centrifugal force and centripetal force
From the study of dynamics we know that, as long as it is a uniform circular motion , the rotating material point is subject to a centripetal force that is directed towards the center of the rotational motion and that allows the point to continue along its own trajectory. circular.
To understand what is the link between centrifugal force and centripetal force , let’s imagine that we have a rotating platform with constant angular velocity , in which a ball is tied with a thread and rotates together with the platform with the exact same angular velocity omega .
For an external observer in an inertial system S, the ball describes a uniform circular motion , in which the tension of the thread acts as a centripetal force and forces the ball to describe a circular path, the only force in play being, in the absence from which the ball would move with a uniform rectilinear motion along the direction tangent to the circular path.
For an observer attached to the non-inertial system S ‘of the platform, the ball is stationary , because it rotates with the same angular velocity as the platform, but the thread is taut. The observer on the platform must then assume that, in addition to the tension in the wire directed toward the center of rotation, there must be another equal and opposite force directed radially outward, so that the sum of the two forces is zero and can explain the fact that the ball remains stationary.
Thus, for the non-inertial observer S ‘, the radially outwardly directed centrifugal force appears. It is also obvious that the centrifugal force is an apparent force because it is not the result of any interaction trying to push the ball out of the platform.
Another example of centrifugal force
We can feel the centrifugal force when we are in the car and facing a curve . If we are in the car and we turn left, we feel pushed out of the car to the right due to centrifugal force.
The car in which we find ourselves is a non-inertial reference system in circular motion with respect to the fixed system of the road.
If we analyze the movement from the point of view of an outside observer, there is nothing that really pushes the passenger out. The passenger is sitting in the seat and is one with the car; Throughout the curve, the friction between the tires and the asphalt acts as a centripetal force and keeps the car (and therefore the passenger) along the circular path.
If we evaluate the situation from the passenger’s point of view, he feels pushed out by the centrifugal force . At the same time, the passenger is also subject to a coercion reaction, being restrained by friction with the seat and by the seat belt.
If we were inside the car, without a seatbelt and without a door, we would see how we got out of the car while turning to the left. The observer would justify this fact by saying that the passenger is not subject to any force and therefore is not able to follow the circular motion of the car along the curve, so it continues with a uniform rectilinear motion along from the tangent to the path.
In summary, the centrifugal force is an apparent force that is only perceived by the non-inertial observer, who is not in a position to perceive the centripetal force. On the other hand, for the inertial observer, the only force that acts is the centripetal force and in no way contemplates the centrifugal force. As usual, there are no right and wrong points of view: the physical model is always the same and the way of describing it changes depending on the chosen reference system.
Centrifugal force applications
Centrifugal force is used in various areas . Just think of a tumble dryer that uses centrifugal action to drain clothes : all the clothes are pushed towards the edge of the drum, compressing and releasing the water absorbed during the wash. Another application refers to the typical centrifuges of chemistry laboratories, which take advantage of the centrifugal action to separate different substances dissolved in solutions.
