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Simple Moment of Inertia Question

by tachu101
Tags: inertia, moment, simple
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tachu101
#1
Jan2-09, 11:33 PM
P: 74
1. The problem statement, all variables and given/known data
A rod of negligible mass is pivoted about one end. Masses can be attached to the rod at various positions along the rod. Currently, there is a mass (m) attached a distance (L) from the pivot. To increase the moment of inertia about the pivot by a factor of 5, you must attach...


2. Relevant equations

I=mr^2

3. The attempt at a solution

Io= mL^2
If= 5(Io) = mL^2(original mass)+4(mL^20) All I did was add four more masses of equal size at a distance L from the pivot. Is there another solution?
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djeitnstine
#2
Jan3-09, 01:05 AM
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You are correct. The definition of moment of Inertia is [tex]\sum_{i} m_{i} r^{2}_{i}[/tex]
Doc Al
#3
Jan3-09, 06:36 AM
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Quote Quote by tachu101 View Post
All I did was add four more masses of equal size at a distance L from the pivot. Is there another solution?
Sure, there are plenty of solutions. The question is a bit vague. Are there any constraints given? (Such as the the number of masses you are allowed to add or the size of the masses.)

For example: What if you could only add a single mass of equal size. How could you solve the problem then?


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