A frame of the reference that is accelerated with respect to an inertial frame of reference is called a non-inertial frame of reference. A coordinate system fixed on a circular disc rotating about a fixed axis with a constant angular velocity $\omega$ is an example of a non-inertial frame of reference. The relationship between the force $\overrightarrow F $
rot experienced by a particle of mass m moving on the rotating disc and the force $\overrightarrow F $
in experienced by the particle in an inertial frame of reference is,
$\overrightarrow F $
rot = $\overrightarrow F $
in + 2m ($\overrightarrow v $
rot $\times$ $\overrightarrow \omega $) + m ($\overrightarrow \omega $ $\times$ $\overrightarrow r $) $\times$ $\overrightarrow \omega $,
where, v
rot is the velocity of the particle in the rotating frame of reference and r is the position vector of the particle with respect to the centre of the disc.

Now, consider a smooth slot along a diameter of a disc of radius R rotating counter-clockwise with a constant angular speed $\omega$ about its vertical axis through its centre. We assign a coordinate system with the origin at the centre of the disc, the X-axis along the slot, the Y-axis perpendicular to the slot and the Z-axis along the rotation axis ($\omega$ = $\omega$ $\widehat k$). A small block of mass m is gently placed in the slot at r = (R/2)$\widehat i$ at t = 0 and is constrained to move only along the slot.
The net reaction of the disc on the block is