## geerky42 3 years ago Four particles at the corners of a square with a side length L = 2m are connected by massless rods (See below) The particle masses are$$m_1 = m_4 = 3$$ kg and $$m_2 = m_3 = 4$$ kg. Find the moment of inertia of the system about the z axis.

1. geerky42

|dw:1359596705890:dw|

2. anonymous

$I = \sum_{i=1}^{n}mi.(ri)^2$

3. anonymous

The trick here is to Choose Orgin..Make Mass ( M3) as Orgin.

4. anonymous

Wait..... I about Z I(z) = I (x) + I (y)

5. geerky42

so r for m3 is zero?

6. geerky42

Sorry, im confused.

7. anonymous

Yup..

8. geerky42

and r for m1 and m4 is L? L√2 for m2, right?

9. anonymous

Yes...u r right..)

10. geerky42

Hmm, I tried this way and i was wrong, guess i should tr again... the key answer is 56 kg*m², by the way.

11. geerky42

try*

12. geerky42

I got it. Thanks.

13. anonymous