Is the Coriolis force a real force?

No, the Coriolis force is an apparent or fictitious force. It only appears to act on objects when their motion is described from within a rotating reference frame. In an inertial (non-rotating) frame, no such force exists; objects continue in straight lines unless acted upon by a real net force, in accordance with Newton's first law.

Why does the puck's path curve to the right in the simulation?

The direction of curvature depends on the direction of the platform's rotation. For a platform rotating counterclockwise (as viewed from above, like the Northern Hemisphere of Earth), the Coriolis effect deflects moving objects to their right. If the platform rotates clockwise, deflection is to the left. The simulator allows you to reverse the rotation to observe this directly.

How does this relate to weather patterns on Earth?

The Earth's rotation creates a rotating reference frame. The Coriolis effect deflects moving air masses—to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection is a key factor in the rotation of large-scale weather systems like cyclones and the prevailing wind patterns known as trade winds and westerlies.

What is the main limitation of this simulator model?

The model assumes a perfectly flat, frictionless rotating plane. On Earth, the Coriolis effect acts on a spherical surface, where the effect's strength varies with latitude (being zero at the equator and maximum at the poles). This simulator uses a constant rotation rate, effectively modeling motion at a single, fixed latitude.

Coriolis Effect

Puck on a rotating platform: curved path in the rotating frame vs straight line inertial.

Live graphs

About this model

A puck slides across a frictionless, uniformly rotating platform. This classic demonstration visualizes the Coriolis and centrifugal effects, which are apparent forces arising in rotating reference frames. In an inertial (non-rotating) frame, the puck obeys Newton's first law, moving in a straight line at constant velocity. However, from the perspective of an observer rotating with the platform, the puck's path appears to curve. This curvature is quantified by the Coriolis acceleration, given by veca_C = -2vecω × vecv, where vecω is the platform's angular velocity vector and vecv is the puck's velocity relative to the rotating frame. The simulator also includes the centrifugal acceleration, veca_cent = -vecω × (vecω × vecr), which pushes objects outward. Key simplifications include a perfectly frictionless surface, uniform rotation, and the omission of other real-world forces like air resistance. By interacting with this model, students can directly explore how the magnitude and direction of the platform's rotation, as well as the puck's initial velocity, alter the observed curved trajectory. This builds a concrete understanding of non-inertial reference frames, vector cross products in physics, and the origin of large-scale phenomena like the deflection of winds and ocean currents on Earth.

Who it's for: Undergraduate physics or engineering students studying classical mechanics, particularly the dynamics of rotating reference frames. It is also valuable for advanced high school students or educators seeking a clear visualization of inertial and non-inertial motion.

Key terms

Coriolis Effect
Rotating Reference Frame
Inertial Frame
Centrifugal Force
Apparent Force
Angular Velocity
Trajectory
Newton's First Law

How it works

On a rotating turntable, a puck sliding without real horizontal forces follows a curved path in the platform frame. In an inertial lab frame that path is a straight line; transforming that line into rotating coordinates reproduces the Coriolis and centrifugal effects you feel in the rotating description.

Key equations

a = −2ω×v − ω×(ω×r) (no real force), ω = Ωk̂

Components: a_x = Ω²x + 2Ωv_y, a_y = Ω²y − 2Ωv_x

Frequently asked questions

Is the Coriolis force a real force?: No, the Coriolis force is an apparent or fictitious force. It only appears to act on objects when their motion is described from within a rotating reference frame. In an inertial (non-rotating) frame, no such force exists; objects continue in straight lines unless acted upon by a real net force, in accordance with Newton's first law.
Why does the puck's path curve to the right in the simulation?: The direction of curvature depends on the direction of the platform's rotation. For a platform rotating counterclockwise (as viewed from above, like the Northern Hemisphere of Earth), the Coriolis effect deflects moving objects to their right. If the platform rotates clockwise, deflection is to the left. The simulator allows you to reverse the rotation to observe this directly.
How does this relate to weather patterns on Earth?: The Earth's rotation creates a rotating reference frame. The Coriolis effect deflects moving air masses—to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection is a key factor in the rotation of large-scale weather systems like cyclones and the prevailing wind patterns known as trade winds and westerlies.
What is the main limitation of this simulator model?: The model assumes a perfectly flat, frictionless rotating plane. On Earth, the Coriolis effect acts on a spherical surface, where the effect's strength varies with latitude (being zero at the equator and maximum at the poles). This simulator uses a constant rotation rate, effectively modeling motion at a single, fixed latitude.

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