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A square plate of mass 120g and edge 5.0...

A square plate of mass 120g and edge 5.00 cm rotates about one of the edges. If it has a unifrom angular acceleration of `0.2 rad/s^2`, what torque acts on the plate?

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The correct Answer is:
A, B
A square plate of mass 120gm and edge 5cm rotates about one of the edge.
Let take a small area of the square of width dx and length a which is at a distance from the axis of rotation.
Therefore, mass of that small area
`=m/a^2=adx`
(m=mass of the square , a=side of the plate)
`l=int_0^a9(m/a)^2xxax^2dx`
`=[(m/a)(x^3/e)]_0^a`
`=[(m/a)(x^3/3)]_)^a=(ma^3/3)`

Therefore torque produced
`=lxxa=((ma^2)/3)xxa`
`={((120xx10^-3xx52xx10^-4))/3.02}`
`=0.2xx10^-1`
`=0.2xx10^-1`
`=2xx10^-5 N-m`
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