On a frictionless surfaces, a block of mass M moving at speed v collides elastically with another block of…
Solution

In elastic collision energy of system remains same. so, \((\mathrm{KE})_{\text {before collision }}=(\mathrm{KE})_{\text {after collision }}\)
Let speed of second body after collision is \(\mathrm{v}^{\prime}\).
$\begin{aligned} & \frac{1}{2} Mv^2+0=\frac{1}{2} M\left(\frac{v}{3}\right)^2+\frac{1}{2} M\left(v^{\prime}\right)^2 \\ & \Rightarrow v^{\prime}=\frac{2 \sqrt{2}}{3} v \end{aligned}$
Asked in: NEET 2015 (Phase 2)
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