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AP EAMCET202018 Sep 2020Evening ShiftPhysicsRotational MotionActual

A light meter rod has two-point masses each of (2 ~kg ) fixed at its ends. If the system rotates about its centre of mass with an angular speed of (0.5 rad s ⁻¹ ), its rotational ( KE ) is

Options

  1. A0.125 erg
  2. B(1.25 erg )
  3. C(1.25 ~J )
  4. D(0.125 ~J )

Correct answer

D. (0.125 ~J )

Step-by-step solution

Total mass of light meter rod including two point masses, (m=(2+2) kg =4 ~kg ) Angular speed, (I=0.5 rad s ⁻¹ ) Length of rod (=1 ~m ) Moment of inertia about centre of mass, (I=2 ( 1 2 )^2+2 ( 1 2 )^2= 2 4 + 2 4 =1 ~kg - m ^2 ) ( ) Rotational kinetic energy (K_ rot = 1 2 I ^2= 1 2 1 (0.5)^2= 0.25 2 =0.125 ~J )

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