1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple Moment of Inertia Question

  1. Jan 2, 2009 #1
    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


    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?
  2. jcsd
  3. Jan 3, 2009 #2


    User Avatar
    Gold Member

    You are correct. The definition of moment of Inertia is [tex]\sum_{i} m_{i} r^{2}_{i}[/tex]
  4. Jan 3, 2009 #3

    Doc Al

    User Avatar

    Staff: Mentor

    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?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Simple Moment of Inertia Question