# Physics

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The moment of inertia of an object depends on the shape of the object, location and orientation of the axis of rotation. For a solid disk, when the disk is rotating about an axis that is perpendicular to the disk and passing through the center of the disk, the moment of inertia is given as I = (1/2)MR2 where M is the mass of the disk and R is the radius of the disk.

(a) If the mass of the disk is 2.4 kg and the radius of the disk is 44 cm, what is the moment of inertia of the disk?
.23232 kg m2

(b) If the disk is rotating at 180 rpm, what is the angular speed of the disk in unit of rad/s? (rpm stands for "round per minute" or "revolution per minute", and is a commonly used unit for rotational speed. Thus, 1 rpm = 2 rad/min = 2/60 rad/s.)

(c) Using the information given in the above questions (a) and (b), calculate the angular momentum of the disk.
kg m2/s

(d) Using the information given in the above questions (a) and (b), calculate the rotational kinetic energy of the disk.
J

I've answered the first two parts but I am not sure how to do last two parts can someone help?

• Physics -

The first two parts are correct.
I=.23232 kg-m²
3)
Angular Momentum = Iω
4)
Rotational kinetic energy = (1/2)Iω²

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