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The moment of inertia of a disc is 5 xx ...

The moment of inertia of a disc is `5 xx 10(-4) kg.m^(2)`. It is rotating freely about a vertical axis passing through its centre at a speed of 40 rpm. A piece of wax of mass 20 g is attached at a distance of 8 cm from its centre. Calculate its new speed.

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The correct Answer is:
32 rpm
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A circular disc rotates at 60 rpm about an axis passing through its centre. A coin of 18 g is placed at a distance of 8 cm from the centre of the disc. Calculate the centrifugal force on the coin.

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Knowledge Check

  • The moment of inertia of a circular disc of mass m and radius r about an perpendicular axis passing through its centre is

    A
    `mr^(2)`
    B
    `(mr^(2))/(4)`
    C
    `(mr^(2))/(2)`
    D
    `(5)/(4) mr^(2)`

  • Moment of inertia of a circular ring of mass m and radius r about the normal axis passing through its centre is

    A
    `(mr^(2))/(4)`
    B
    `mr^(2)`
    C
    `(mr^(2))/(2)`
    D
    `(3)/(2) mr^(2)`

  • Radius of gyration of a disc of mass 50 g and radius 0.5 cm about an axis passing through its centre of gravity and perpendicular to the plane is

    A
    6.54 cm
    B
    3.64 M
    C
    0.35 cm
    D
    0.88 cm

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    What is the moment of inertia of a solid sphere (radius = r mass =m ) about an axis passing through any of its diameters ?

    Find (i) the moment of inertia of a rod of mass 100 g and length 100 cm about and axis passing through its centre and perpendicular to its length and (ii) the radius of gyration.

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    A conducting sphere of radius 5 cm has a charge of 20 esu. What is the electric potential at a distance of 10 cm away from its centre?

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