Posted by **Jake** on Thursday, March 4, 2010 at 11:40pm.

The figure below

shows an arrangement of 15 identical disks that have been glued together in a rod-like shape of length L = 1.4500 m and (total) mass M = 135.000 g. The arrangement can rotate about a perpendicular axis through its central disk at point O.

(a) What is the rotational inertia of the arrangement about that axis?

(b) If we approximated the arrangement as being a uniform rod of mass M and length L, what percentage error would we make in using the formula in Table 10-2e to calculate the rotational inertia?

%

the formula given is I=1/12 ML^2

- Physics. -
**drwls**, Friday, March 5, 2010 at 7:56am
I don't quite get the picture here. The exact moment of inertia, for rotation about an axis that is perpendicular to the axis of the glued-together rod, will depend upon the diameter of the discs as well as the length of the rod. I don't get the significance of the number of discs, since they are glued together into one road.

The formula I = (1/2) m L^2 applies to a rod that is very narrow compared to its length, and rotated about its center, about an axis PERPENDICULAR to the axis of the rod

## Answer this Question

## Related Questions

- Physics helppp - The figure below shows an arrangement in which four disks are ...
- physics - two small objects of masses 'm' & '2m' each are attaached to the ends ...
- Physics, please help today! - 0.0100kg particles have been glued to a rod of ...
- physics - A uniformly charged insulating rod of length 13.0 cm is bent into the ...
- Physics - Consider the rods plus disc system shown in the Figure. The rod has a ...
- physics - The figure shows an arrangement in which four disks are suspended by ...
- Physics - As shown in the figure below, cars #1 and #2 are sliding across a ...
- Physics Please Help Today Part 2 - Here's a pic C:\Documents and Settings\Owner\...
- physics - Jahna and Raul move onto the setup for experiment 2. They have been ...
- college physics - I don't know where to begin with this question. Could someone ...