A ring of mass M and radius R is rotating with angular speed ω about a fixed vertical axis passing through…

A ring of mass M and radius R is rotating with angular speed ω about a fixed vertical axis passing through its centre O with two point masses each of mass M8 at rest at O. These masses can move radially outwards along two massless rods fixed on the ring as shown in the figure. At some instant the angular speed of the system is 89ω and one of the masses is at a distance of 35R from O. At this instant the distance of the other mass from O is (if we are getting two correct answers, mark one with higher value)

  1. 23R
  2. 13R
  3. 35R
  4. 45R

Solution

Using conservation of angular momentum about axis of ring
MR2ω=MR289ω+M8925R289ω+Mr2889ω 
r=4R5 ^

Asked in: JEE Advanced 2015 (Paper 1)

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