Coriolis effect

Figure 1: In the inertial frame of reference (upper part of the picture), the black object moves in a straight line. However, the observer (red dot) who is standing in the rotating (non-inertial) frame of reference (lower part of the picture) sees the object as following a curved path.

In physics, the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame.

Newton's laws of motion govern the motion of an object in an inertial frame of reference. When transforming Newton's laws to a rotating frame of reference, the Coriolis force appears, along with the centrifugal force. If the rotation speed of the frame is not constant, the Euler force will also appear. All three forces are proportional to the mass of the object. The Coriolis force is proportional to the speed of rotation and the centrifugal force is proportional to its square. The Coriolis force acts in a direction perpendicular to the rotation axis and to the velocity of the body in the rotating frame and is proportional to the object's speed in the rotating frame. The centrifugal force acts outwards in the radial direction and is proportional to the distance of the body from the axis of the rotating frame.

These three additional forces are termed either inertial forces, fictitious forces or pseudo forces. These names are used in a technical sense, to mean simply that these forces vanish in an inertial frame of reference.