Question

Four 2 kg masses are located at the corners of a square of sides 25 cm. What is the moment of inertia of the array about an axis through one of the masses and perpendicular to the plane of the four masses?

Answer 1

\[I=m _{1}r _{1}^{2}+m _{2} r _{2}^{2}+m _{3}r_{3}^{2}\]where r is the perpendicular distance of the mass from the rotation axis\[I=2kg(.25m)^{2} +2kg(.25m)^{2}+2kg(.25m)^{2}\]

Answer 2

sorry - one of those distances should be 1.414*.25m so\[I=2kg(.25m)^{2} +2kg(\sqrt{2} \times .25m)^{2} +2kg(.25m)^{2} \]

Answer 3

so the answer should be 0.43 then?

Answer 4

right

Answer 5

cool! Thank-you so much. It makes more sense now. ;D