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Stuck here, help me understand: A thin horizontal circular disc is rotating about a vertical axis passing through its centre. An insect is at rest at a point near the rim of the disc. The insect now moves along a diameter of the disc to reach its other en

A thin horizontal circular disc is rotating about a vertical axis passing through its centre. An insect is at rest at a point near the rim of the disc. The insect now moves along a diameter of the disc to reach its other end. During the journey of the insect, the angular speed of the disc

Option 1)

remains unchanged

Option 2)

continuously decreases

Option 3)

continuously increases

Option 4)

first increases and then decreases

Answers (1)
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As we learnt in

Rotational angular momentum -

\vec{L}= I\vec{w}

 

- wherein

I = Moment of inertia about fixed axis of rotation

w = angular velocity of rotation

 

 

 First - increases (towards the centre)

then - decreases (away from the centre)

We know that v=\omega\ r

\omega\ \alpha \;\frac{1}{r}

Ans. 4


Option 1)

remains unchanged

This is an incorrect option.

Option 2)

continuously decreases

This is an incorrect option.

Option 3)

continuously increases

This is an incorrect option.

Option 4)

first increases and then decreases

This is the correct option.

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