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Coin or beaker on a rotating disc: condition on angular velocity or distance for it not to slip

This type of question, asked 2 times: 25 Jun 2022, 31 Jan 2024. All 2 questions below, oldest first.

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  1. Question 1

    25 Jun 2022

    93
    A disc with a flat small bottom beaker placed on it at a distance RR from its center is revolving about an axis passing through the center and perpendicular to its plane with an angular velocity ω\omega. The coefficient of static friction between the bottom of the beaker and the surface of the disc is μ\mu. The beaker will revolve with the disc if:

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  2. Question 2

    31 Jan 2024

    17
    A coin is placed on a disc. The coefficient of friction between the coin and the disc is μ\mu. If the distance of the coin from the center of the disc is rr, the maximum angular velocity which can be given to the disc, so that the coin does not slip away, is :

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