Question

Three bricks each of length L and mass M are arranged as shown from the wall. The distance of the centre of mass of the system from the wall is

• A. L/4
• B. L/2
• C. (3/2)L
• D. (11/12)L

Answer 1

The correct option is D (11/12)L

$x_1=\frac{L}{2}$, $x_2=\frac{L}{2}+\frac{L}{2}=L$ and $x_3=\frac{L}{2}+\frac{L}{4}+\frac{L}{2}=\frac{5}{4}L$

Therefore,

$X_{cm}=\frac{m_1{x}_1+m_2{x}_2+m_3{x}_3}{m_1+m_2+m_3}$

$=\frac{M\times \frac{L}{2}+M\times L+M\times \frac{5L}{4}}{M+M+M}$

$\frac{\frac{11}{4}ML}{3M}=\frac{11}{12}L$