Moment of Inertia Using Parallel Axis Theorem

[woaini]

Homework Statement

Q is the edge length of the cube. The moment of inertia of the cube about an axis passing through its center and the center of two opposing faces is (1/6)mQ^2 (PCM in the diagram). Use the parallel axis theorem to find the moment of inertia if the axis is along one face of the cube (Pface).

PCM=(1/6)mQ^2
Pface=?
d=?

Homework Equations

Pface = PCM+md^2

The Attempt at a Solution

d=(1/2)Q^2

Pface=$\frac{mQ^2}{6}$+$\frac{mQ^2}{4}$

Pface=$\frac{5mQ^2}{12}$

 

[Tanya Sharma]

Homework Statement

Q is the edge length of the cube. The moment of inertia of the cube about an axis passing through its center and the center of two opposing faces is (1/6)mQ^2 (PCM in the diagram). Use the parallel axis theorem to find the moment of inertia if the axis is along one face of the cube (Pface).

PCM=(1/6)mQ^2
Pface=?
d=?

Homework Equations

Pface = PCM+md^2

The Attempt at a Solution

d=(1/2)Q^2

Pface=$\frac{mQ^2}{6}$+$\frac{mQ^2}{4}$

Pface=$\frac{5mQ^2}{12}$

Correct...except d = Q/2