Question

A thin horizontal circular disc is rotating about a vertical axis passing through it's 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 . [AIEEE 2011]
(a) continuously decrease
(b) continuously increase
(c) first increase and then decreases
(d) remains unchanged ​

Answer 1

Answer:

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Answer 2

Explanation:- We know that moment of inertia of circular disc is 1/2MR²

By parallel axis theorem .

Moment of inertia , I = 1/2MR² + mx²

• where, m = mass of insect ,and x = distance of insect from centre , clearly as the insect moves along the diameter of the disc ,moment of inertia first decrease , then increases .

By conservation of Angular momentum , Angular speed first increases then decreases .

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