Question

http://prntscr.com/tm3me9
Explain the solution.
Thanks

Answer 1

Initial momentum = final momentum

$mv=2mu\cos45°\to u=\frac{v}{2\cos45°}=\frac{v}{2\cdot\frac{\sqrt{2}}{2}}=\frac{v}{\sqrt{2}}$ (c) Answer.