Posted by **Suroj** on Wednesday, January 9, 2013 at 3:40am.

a circular disc rotates on a thin air film with a period of 0.3s. its moment of inertia about its axis of rotation is 0.06kgm^2. a small mass is dropped onto th disc and rotates with it . the moment of inertia of the mass about the axis of rotation is 0.04kgm^2.determine the final period of rotating the disc and mass?

- Physics -
**drwls**, Wednesday, January 9, 2013 at 6:33am
The answer depends upon where the mass is dropped, but since they tell you the moment of inertia of the dropped mass about the axis, that is enough to answer the question.

Angular momentum about the axis is conserved. The original angular velocity of the disc is

w1 = 2 pi/(period1) = 20.9 rad/s

Period is inversely proportional to angyualr velocity

If w2 is the final angular velocity,

I1*w1 = (I1 + I2)*w2

w2 = (0.06/0/10)*w1 = (3/5)*w1

Period2 = (5/3)*w1 = 0.5 seconds

## Answer This Question

## Related Questions

- physics - a circular disc rotates on a thin air film with a period of 0.3s. its ...
- Physics - Consider a rod plus disc system. The rod has a total length L =1.30 m...
- Physics - A student puts on a Dresden Dolls disc in her cd player which spins at...
- Physics - A student puts on a Dresden Dolls disc in her cd player which spins ...
- physics - from a disk of radius R,a concentric circular portion of radius r is ...
- physics - A student puts on a Dresden Dolls disc in her cd player which spins at...
- physics - a disc of radius 5.70 cm rotates about its axis and a point 1.90 cm ...
- physics - a disc of radius 5.70 cm rotates about its axis and a point 1.90 cm ...
- Physics - Consider the rods plus disc system shown in the Figure. The rod has a ...
- physics - A horizontal disc rotating freely about a vertical axis makes 90 ...

More Related Questions