Question

Two carts on horizontal straight rails are pushed apart by an explosion of a point charge $Q$ placed between the carts. Suppose the coefficient of friction of the two are equal and $200\text{kg}$ cart travels a distance of $36\text{m}$ and stops. The distance covered by the cart weighing $300\text{kg}$ is

• A. $12\text{m}$
• B. $16\text{m}$
• C. $24\text{m}$
• D. $32\text{m}$

Answer 1

The correct option is C $24\text{m}$

Since net external force on the system containing the two masses is zero, the position of centre of mass does not change.
$m_1{s}_1=m_2{s}_2$
$\therefore 300\times s_1=200\times 36$
$\therefore s_1=24m$

Why this question? "In the absence of an external force on a system, the position of centre of mass of a system is unaltered no matter how the internal forces act."