Question

Two blocks of masses $10 \,kg$ and $30\, kg$ are placed on the same straight line with coordinates $(0,0) cm$ and $( x , 0) cm$ respectively. The block of $10\, kg$ is moved on the same line through a distance of $6\, cm$ towards the other block. The distance through which the block of $30\, kg$ must be moved to keep the position of centre of mass of the system unchanged is :

• A. $4 \,cm$ towards the $10 \,kg$ block
• B. $2\, cm$ away from the $10 \,kg$ block
• C. $2\, cm$ towards the $10 \,kg$ block
• D. $4 \,cm$ away from the $10\, kg$ block

Answer 1

Answer: (C)

$\Delta x_{G}=\frac{m_{1} \Delta x_{1}+m_{2} \Delta x_{2}}{m_{1}+m_{2}}$
$0=\frac{10 \times 6+30\left(\Delta x_{2}\right)}{40}$
$\Delta x_{2}=-2 \,cm$
Block of mass $30\, kg$ will to move towards $10 \,kg$.