moment of inertia

[Mahmoud]

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?

thanks in advance

[photomark]

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]

1/3 ML^2 is correct

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

The integral reduces to the above equation.

[Mahmoud]

ok then he writes wrongly or he has something else in his mind