Question

Four masses are fixed on a massless rod as shown in figure. The moment of inertia about the axis $P$ is given as:

• A. $2kg$ $m^2$
• B. $1kg$ $m^2$
• C. $5kg$ $m^2$
• D. $0.3kg$ $m^2$

Answer 1

The correct option is B $1kg$ $m^2$

Distance of $5kg$ from axis $r_1=0.2m$

Distance of $2kg$ from axis $r_2=0.4m$

Moment of inertial $I=2\times r_2^2+5\times r_1^2+5\times r_1^2+2\times r_2^2$

$⟹I=2\times {0.4}^2+5\times {0.2}^2+5\times {0.2}^2+2\times {0.4}^2=1.04kg{m}^2$