A thin horizontal circular disc is rotating about a vertical axis pass...
Angular momentum L=Iω
L=mr2×ω
Since r first decreases then increases.
So due to conservation of angular momentum L first increases then decreases.
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A thin horizontal circular disc is rotating about a vertical axis pass...
Explanation:
When the insect moves along the diameter of the disc, it causes a shift in the distribution of mass of the disc. This shift in the distribution of mass causes a change in the moment of inertia of the disc.
Initially, the moment of inertia of the disc is given by:
I = (1/2)MR^2
Where M is the mass of the disc and R is the radius of the disc.
When the insect moves along the diameter of the disc, the moment of inertia of the disc changes. Let the new moment of inertia of the disc be I'. The new moment of inertia of the disc can be given by:
I' = (1/4)MR^2 + 2m(d/2)^2
Where m is the mass of the insect and d is the distance of the insect from the centre of the disc.
As the insect moves towards the centre of the disc, d decreases, and hence, the moment of inertia of the disc increases. Therefore, the angular speed of the disc decreases to conserve angular momentum.
As the insect moves towards the other end of the diameter, d increases, and hence, the moment of inertia of the disc decreases. Therefore, the angular speed of the disc increases to conserve angular momentum.
Hence, the angular speed of the disc first increases and then decreases when the insect moves along a diameter of the disc to reach its other end.
A thin horizontal circular disc is rotating about a vertical axis pass...
Our system is :--> Disc + Insect
As external torque is zero , which means (tau = 0)
So , angular moment is conserved
From, conservation of angular momentum
I1W1 = I2W2
When insect is moving from edge to centre , then r will be decrease and w(angular velocity) will be increse.
When insect is moving from centre to edge , then r will be increase and w(angular velocity) will be decrease.
So, here correct answer is option (C) that is "First increase and then decreases"...
$$Hope it's help... $$
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