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Work, Energy And Power For Rotating Body - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

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  • 16 Questions around this concept.

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If 'I' is the moment of inertia of a body and 'w' is its angular velocity, the rotational kinetic energy of the body is 

A body of M.I. 3 kg $m^2$ rotating with an angular velocity 2 rad/s has the same K.E. as a mass of 12 kg moving with a velocity of

A thin hollow sphere of mass m is completely filled with an ideal liquid of mass m. When the sphere rolls with a velocity v kinetic energy of the system is equal to

 

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

Concepts Covered - 1

Work, Energy and Power for Rotating Body
  1. Work-

For translation motion

$
W=\int F d s
$


So for rotational motion

$
W=\int \tau d \theta
$
 

  1. Rotational kinetic energy-

The energy of a body has by virtue of its rotational motion is called its rotational kinetic energy.

 

    

 

Rotational kinetic energy

Translatory kinetic energy

1

K_R=\frac{1}{2}I\omega ^2

  

K_T=\frac{1}{2}mV ^2

 

2

K_R=\frac{1}{2}L\omega

  

K_T=\frac{1}{2}PV

 

3

K_R= \frac{L^2}{2I}

 

K_T= \frac{P^2}{2m}

 

 

  1. Power =Rate of change of kinetic energy  

 

For translation motion $P=\vec{F} \cdot \vec{V}$
So for rotational motion

$
P=\frac{d\left(K_R\right)}{d t}=\frac{d\left(\frac{1}{2} I \omega^2\right)}{d t}=I \omega \frac{d \omega}{d t}=I \alpha \omega=\tau \cdot \omega
$


Or $P=\vec{\tau} \cdot \vec{\omega}$

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Work, Energy and Power for Rotating Body

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