Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
Manipal MET2021PhysicsRotational Motion

A uniform thin bar of mass 6 m and length 12 L is bent to make a regular hexagon. Its moment of inertia about an axis passing through the centre of mass and perpendicular to the plane of hexagon is :

Options

  1. A20 ~mL ^2
  2. B30 ~mL ^2
  3. C12 5 mL^2
  4. D6 ~mL ^2

Correct answer

A. 20 ~mL ^2

Step-by-step solution

Length of each side of hexagon =2 L and mass of each side =m Let O be the centre of mass of hexagon. Therefore, perpendicular distance of O from each side, r=L 60^ =L 3 The desired moment of inertia of hexagon about O is aligned I & =6 [I_ one side ]=6 [ m(2 L)^2 12 +m r^2 ] & =6 [ mL^2 3 +m(L 3 )^2 ] & =20 mL^2 aligned

Practice Rotational Motion on Quantrex Academy →

More from Rotational Motion

A bullet, fired into a door gets embedded exactly at it's centre, causing the door to rotate about it's vertical axis, practically without friction, with an angular velocity of 0.6 2026A singer, during his performance, stands on the edge of a circular turntable, and begins to walk along its edge with a speed of 1.5 ms⁻¹ relative to the ground. The turn table is m 2026A particle starts rotating from rest. The instantaneous angular displacement is = 3t^3 - t^2 , where is in radian and t in s; The angular velocity at t = 1 s is 2026Four masses each 2 kg are placed at the corners A, B, C, D of a mass less square frame. 40 kg mass is at the centre O of a square frame of side 0.2m. It is to be rotated about an a 2026The position of a particle of mass 1 kg at time t is given by r = t , i + j + 2t^2 , k , where t is in seconds and the coefficients have the proper units for r to be in metres. Wha 2026The angular momentum of a moving body remains constant, if 2026If the earth were to suddenly contract to half of its present radius, what would be the duration of the day? 2026The angular velocity of a body changes from 6 rad s ⁻¹ to 21 rad s ⁻¹ in a time of 1.5 s. If the moment of inertia of the body is 100 ~g ~m ^2 , then the rate of change of angular 2025 Full Rotational Motion list All Manipal MET PYQs