# PHYSICS

posted by
**wolfpak** on
.

The masses and coordinates of four particles are as follows: 40 g, x = -4.0 cm, y = 5.0 cm; 30 g, x = 5, y = 0.0 cm; 40 g, x = –5.0 cm, y = 3.0 cm; 20 g, x = 3.0 cm, y = 2.0 cm. What are the rotational inertias of this collection about the (a) x, (b) y, and (c) z axes?

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So I used Rotational Inertia = mL^2

For x I did: (40)(-4)^2+(30)(5)^2+(40)(-5)^2+(20)(3)^2

After adding these up I have 2570 g*cm^2 which is the wrong answer. Can you please point me in the right direction? thanks!

well, you did the one for rotation about x=0, the y axis, not the x axis. The numbers are correct.

AH! Thank you!!!