Question

Four spheres of diameter 2a and mass M are placed with their centres on the four corners of a square of side b. Then the moment of Inertia of the system about an axis along one of the sides of the square is

• A. $\frac { 4 } { 5 } \mathrm { Ma } ^ { 2 } + 2 \mathrm { Mb } ^ { 2 }$
• B. $\frac { 8 } { 5 } \mathrm { Ma } ^ { 2 } + 2 \mathrm { Mb } ^ { 2 }$
• C. $\frac { 8 } { 5 } \mathrm { Ma } ^ { 2 }$
• D. $\frac { 4 } { 5 } \mathrm { Ma } ^ { 2 } + 4 \mathrm { Mb } ^ { 2 }$

Answer 1

Answer: (B)

$\frac { 8 } { 5 } \mathrm { Ma } ^ { 2 } + 2 \mathrm { Mb } ^ { 2 }$

Answer 2

I = $\left[ \frac { 2 } { 5 } \mathrm { Ma } ^ { 2 } \right]$ × 2 + $\left[ \frac { 2 } { 5 } \mathrm { Ma } ^ { 2 } + \mathrm { Mb } ^ { 2 } \right]$× 2