First slide
Rotational motion

A disc of radius r = 20 cm is rotating about its axis with an angular speed of 20 rad s-1. It is gently placed on a horizontal surface which is perfectly frictionless (Fig). What is the linear speed of point A on the disc (in m/s)?


Since the surface is perfectly frictionless, the disc will not roll on the surface; it will simply keep on rotating at point B where it is placed. Now

Linear speed = distance from centre × angular speed

Given, r=20cm=0.2m and ω=20rads1

Linear speed at point A=OA×ω==0.2×20=4 ms-1.

Get Instant Solutions
When in doubt download our app. Now available Google Play Store- Doubts App
Download Now
Doubts App