### Author Topic: moment of inertia  (Read 2570 times)

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#### Mahmoud

• Jr. Member
• Posts: 24
##### moment of inertia
« on: October 26, 2010, 12:44:55 PM »
i read robot arm article and it says that the moment of inertia of the arm is m*d^2 and i think it is supposed to be 1/3 m*d^2 because it is a rod rotating about its end
please can any one help me?

#### photomark

• Jr. Member
• Posts: 44
##### Re: moment of inertia
« Reply #1 on: October 27, 2010, 04:43:25 AM »
The moment of inertia can not be solved with either of them formulas .calculating mass moment of inertia requires integrals and is not easy unless you are a whiz at calculus .

Do you mean the moment around a point ?

The formula for this is M=f*d  for example if you have a lever with a (d) 500 mm (0.5m) long and at the end of that lever you apply a force of 100N then the moment around the end of the lever is 0.5 *100 = 50N.m . also known as torque .

#### SickSpeedMonte

• Beginner
• Posts: 6
##### Re: moment of inertia
« Reply #2 on: October 27, 2010, 10:24:20 AM »
1/3 ML^2 is correct

http://hyperphysics.phy-astr.gsu.edu/hbase/mi2.html

The integral reduces to the above equation.

• Jr. Member
• Posts: 24