# Centrifugal Force vs Coriolis Force: 3 Important Facts

Both Centrifugal Force and Coriolis Force appear as fictitious or pseudo forces by treating an accelerating frame of reference as an inertial one.

Centrifugal Force and Coriolis Force come into existence when Newton’s Laws of motion are applied to a rotating frame of reference rather than an inertial one. The relative forces are proportionate to the masses of huge objects when applied. But there are a plenty of ways which differentiate them in various aspects. Let us take a look at some examples of Centrifugal Force vs Coriolis Force.

## Differences between Centrifugal Force and Coriolis Force

Both Centrifugal Force and Coriolis Force are pseudo forces, yet they are different in the ways they are conceptualized.

## Merry-go-round

Merry-go-round in the children’s park is an example where both the forces can be experienced.

A tangential velocity vector generates a force that appears to pull a person outward, when standing on the edge of a merry-go-round. This is the Centrifugal Force. If an object remains stationary with respect to the Earth reference frame but starts flying above the merry-go-round, then an apparent force comes into play, that tends to divert it sideways even if it keeps traveling in a straight line towards the axis of rotation. This apparent force is called Coriolis Force.

## Rotation of the Earth

We’ll now discuss the fictitious forces caused by the earth’s rotation, because the earth’s surface isn’t truly an inertial frame.

It is commonly observed that Coriolis Force tends to deflect every object towards the right side, that travels on the surface of the Earth in the northern hemisphere. This same phenomenon causes the water to appear in a counterclockwise motion when the drainage of the water out of the bathtub is observed from the top. But rotation of the Earth around a fixed axis causes the Centrifugal Force to always act radially outward from the axis. It appears to oppose the gravity at the equator, while it is zero at the poles.

## Direction of Wind

Movement of a fluid from one latitude to other causes it to experience difference in its distance from the axis of rotation. This is compensated through the maintenance of the angular momentum at a steady value by changing  the rate of rotation of the axis.

The Coriolis Force always acts at a right angle to the wind vector and is directly proportional to its speed. On the other hand, the wind speed determines the magnitude of the Centrifugal Force, which is proportionate with the reciprocal of radius of curvature.

Let us elaborate the CorioIis Effect in further detail. Moving in the eastward direction causes the air to flow faster than the speed required to keep intact with the surface of the Earth. It also moves perpendicularly with the axis of rotation. The air, upon being pulled back towards the centre of the Earth by gravity, causes it to flow towards the equator.

When air flows westward, it moves slower than air that stays at the same distance from the axis of rotation and so moves perpendicular to the axis. The ground, however, gets in the way, and the slope of the surface pushes it toward the poles.

Coming to the Centrifugal Force, when air is pushed into the centre of a low-pressure centre, it curves, causing the force to be directed outward. When air is pushed away from a high-pressure point, it curves, causing a Centrifugal Force to be directed outward. The Centrifugal Force component is always directed away from the centre of curvature of the wind.

## Foucault Pendulum

The Foucault pendulum, which may occasionally be seen in the lobbies of large prominent buildings, is another example of how the Coriolis Force is useful.

As seen from above, the plane in which the pendulum swings back and forth steadily rotates in a clockwise manner. The Coriolis Force pushes the pendulum to the right as it swings across. On the way back, it is likewise pulled to the right, which simply turns the pendulum’s plane in a clockwise direction. The Foucault pendulum is a visually spectacular representation of the earth’s rotation.

## Meteorological Effects

The centrifugal and Coriolis Forces are introduced to accommodate the tentative postulation of a rotating frame of reference with the earth stationary.

The appropriate Rossby numbers in the large-scale dynamics of the oceans and atmosphere determine their relative importance. High values of Rossby number in tornadoes result in stronger Centrifugal Force components in them, with very small amount to almost non-existent Coriolis effect.

The spiraling pattern in these gyres is created by the deflection generated by the Coriolis effect, even though the circulation is not as strong as in the air.

## Terrestrial Effects

The Coriolis influence causes strong features like jet streams and western boundary currents to arise, where it is subjected to geostrophic balancing with pressure gradient.

Many forms of waves, including Rossby waves and Kelvin waves, propagate in the ocean and atmosphere due to Coriolis acceleration. The Ekman Dynamics found in large water bodies like oceans and a hugely spanned water flow pattern in them called the Sverdrup balance, are called impacted by the Coriolis effect.

## Eötvös Effect

The practical impact of the Coriolis Effect is established by the horizontal vector component of the horizontal motion acceleration.

Things heading westward are deflected downwards, while objects travelling eastward are deflected upwards. The Eötvös effect is the name for this phenomenon. Near the equator, this part of the Coriolis effect is most prominent. The Eötvös effect force analogous to the horizontal component does not create any significant impact on the hydrostatic equilibrium, owing to pressure and gravity.

Winds, on the other hand, are related with tiny pressure departures from hydrostatic equilibrium in the atmosphere. Because the order of magnitude of pressure variations in the tropical atmosphere is so small, the Eötvös effect has a significant impact on pressure deviations.

## Ballistic Trajectories

In external ballistics, the Coriolis Force is useful for estimating the trajectories of very long-range artillery projectiles

The Coriolis Force alters the trajectory of a bullet in minute ways, impacting accuracy over vast distances. Snipers make accurate aims from large distances which can compensate for the effect of the Coriolis Force. The force vector acting perpendicular to the point of origin causes low hits towards the west and high hits towards the east, as witnessed in the Eötvös effect in the section above.

The curvature of missile, satellite, and similar object tracks when depicted on two-dimensional maps should not be confused with the effects of the Coriolis Force on ballistic trajectories. The Paris gun, which was employed by the Germans to shell Paris from a range of around 120 kilometres during World War I, is the most renowned historical example.

## What is Centrifugal Force?

The effect of Centrifugal Force has significant mentioning in Newtonian Mechanics, for all objects found in a rotating reference frame.

Centrifugal Force acts on all objects under the effect of inertia that are observed in a rotating frame of reference. This force vector moves through the origin of a coordinate system and acts outwards from an axis that is parallel to the rotation axis of the coordinate system. The direction of this vector goes radially outwards from the axis of rotation upon passing through the origin.

## What is Coriolis Force?

The first conceptual evidence of Coriolis Effect has been found in a scientific journal paper from 1835, that was composed by Gaspard-Gustave de Coriolis, while already working on the theory of water wheels.

Any object that moves within a rotating reference frame in regards with an inertial frame is impacted by the Coriolis Force. Clockwise rotation of the object causes this force vector to direct towards the left of the frame of reference. The impact of this force is significant towards the right direction in the counterclockwise rotation. The Coriolis Force causes an object to deflect from its original path and this phenomenon is called the Coriolis effect.

## Is Centrifugal Force real?

Any force with an unknown source of origin is considered as a fictitious force.

An object experiences Centrifugal Force while subject to a rotating frame of reference, without any external force working on it whatsoever. This implies that Centrifugal Force opposes the Centripetal Force, without any known cause of its origin. It appears to act on isolated objects and hence, it is not considered real.

## Is Coriolis Force real?

No, Coriolis force is not real because it is a pseudo force.

Just like the Centrifugal Force, the Coriolis is only real as long as it accounts for an object in a rotating frame of reference. It is a fictitious force, if observed otherwise.

## Why Coriolis Force is zero at the Equator?

Zero sense of rotation of the Earth’s surface nullifies the effect of the Coriolis factor.

Any object that is placed horizontally on the Equator and is free to move at that particular surface, follows a straight path with no curving in regards with the surface of the Earth. Hence, no Coriolis Effect is experienced at the Equator.

Esha Chakraborty

I have a background in Aerospace Engineering, currently working towards the application of Robotics in the Defense and the Space Science Industry. I am a continuous learner and my passion for creative arts keeps me inclined towards designing novel engineering concepts. With robots substituting almost all human actions in the future, I like to bring to my readers the foundational aspects of the subject in an easy yet informative manner. I also like to keep updated with the advancements in the aerospace industry simultaneously. Connect with me with LinkedIn - http://linkedin.com/in/eshachakraborty93