I'm having some problems doing my homework. Please help me.(adsbygoogle = window.adsbygoogle || []).push({});

1. Three rods, each of length L and mass M, are welded together perpendicularly (like an x-y-z coordinate system). The axis of rotation is drawn in pink in the image below. I have to find the moment of inertia.

I used the parallel-axis theorem to get:

I = I-cm + MD²

I = 2(.5ML²) + M(L/2)²

I = (5/4)ML²

I'm not sure if I'm right, could someone check my method?

2. Picture 2 is a car tire. It has two sidewalls (gray) of uniform thickness 0.635 cm and a tread wall (cyan) of uniform thickness 2.5 cm and width 20.0 cm. Its density is uniform, with a value of 1.10E3 kg. Find its moment of inertia about an axis through its center, perpendicular to the plane of the sidewalls. (A = 16.5 cm, B = 30.5 cm, C = 33.0 cm).

I have no idea what to do.

3. What values would you need to estimate the moment of inertia of your body as you stand tall and turn in a vertical axis passing through the top of your head to the point between your feet?

Again, I have no idea what to do.

Thanks in advance.

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# Homework Help: Moment of Inertia for three rods

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