A wheel of mass 2 kg having practically all the mass concentrated along the circumference of a circle of radius 20 cm, is rotating on its axis with an angular velocity of 100 rad/s. The rotational kinetic energy of the wheel is

  • Option 1)

    4 J

  • Option 2)

    70 J 

  • Option 3)

    400 J

  • Option 4)

    800 J

 

Answers (1)

As we learnt in

Kinetic energy of rotation -

K=\frac{1}{2}Iw^{2}

- wherein

I = moment of inertia about axis of rotation

w = angular velocity

 

 K_{rot}=\frac{1}{2}I \omega^{2}=\frac{1}{2}mr^{2}\omega^{2}

K_{rot}=\frac{1}{2}\times 2\times 400\times 10^{-4}\times100\times 100

K_{rot}=400J


Option 1)

4 J

This solution is incorrect 

Option 2)

70 J 

This solution is incorrect 

Option 3)

400 J

This solution is correct 

Option 4)

800 J

This solution is incorrect 

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