Question

A solid cylinder of radius R and length L have moment of inertia I1 and a second solid cylinder of radius R2 and length L2 cut from it have moment of inertia I2. Find 11/I2.

• A. 64
• B. 32
• C. 128
• D. 256

Answer 1

Answer: (B)

32

Answer 2

I1 = M($(\frac{R^2}{4})$+$(\frac{L_2}{12})$)
I1 = $(\frac{M}{4})$(R2+$(\frac{L^2}{3})$)
M = ρπR2L
M2 = ρπ$(\frac{R^2}{8})$L = $\frac{M}{8}$
I2 = $(\frac{M}{8})$x($(\frac{1}{4})$[$(\frac{R^2}{4})$+$(\frac{L_2}{12})$]
= $(\frac{M}{128})$[R2+$(\frac{L_2}{3})$]