Sunday

February 1, 2015

February 1, 2015

Posted by **Trace** on Wednesday, January 19, 2011 at 7:48pm.

A CD has a diameter of 12.0 cm and a mass of 15.8 g. The motor in a CD player causes the disk, initially at rest, to spin. When in operation, the CD spins in such a way that the laser scans the tracks at a constant tangential velocity of 1.20 m/s. The first track of the CD is at a radius of 20.0 mm from the centre of the disk. Calculate the work done by the motor in the CD player in bringing the disk from rest to the proper speed to read the first track. You may ignore the small circular hole at the CD’s centre. [Hint: Recall the work-kinetic energy theorem.]

I got an angular speed of 60 rad/s, and now I'm trying to figure out the moment of inertia (I) so I can use the formula K rotational = 1/2 I w^2, then I should be able to equate work with kinetic energy using the formula K final = K initial + work, where K initial is zero.

but I don't know how to find moment of inertia. Do I just use the total mass of the cd given?

**Answer this Question**

**Related Questions**

physics - Suppose that you measured the moment of inertia of the system as I = 5...

PHYSICS - A flywheel in the form of a heavy circular disk of diameter 0.83 m and...

Physics. PLEASE HELP!! - A 1.2 m diameter wagon wheel consists of a thin rim ...

physics - A flywheel in the form of a heavy circular disk of diameter 0.83 m and...

Physics - What is the moment of inertia of an object that rolls without slipping...

Physics hw question mistake - Hello, I didn't post the correct questions ...

Physics please check - A rotating door is made from four rectangular glass panes...

physics please help - A rod with a diameter of 1.8 cm is used to make the letter...

College Physics - College Physics- Inertia? Find the moment of inertia about ...

12th grade - A bicycle wheel has a radius of 0.330 m and a rim whose mass is 1....