A boy ties a stone of mass 100   g to the end of a 2   m long string and whirls it around in a…

A boy ties a stone of mass 100 g to the end of a 2 m long string and whirls it around in a horizontal plane. The string can withstand the maximum tension of 80 N. If the maximum speed with which the stone can revolve is Kπ rev min-1. The value of K is :
(Assume the string is massless and un-stretchable)
  1. 400
  2. 300
  3. 600
  4. 800

Solution

The maximum angular velocity of the stone is ω=rpm×2π60=K30 rad s-1

The tension in the string will provide the required centripetal force. Therefore,

T=mω2l80=0.1×K302×2K2=360000K=600

Asked in: JEE Main 2022 (24 Jun Shift 1)

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