Question

A particle of mass $m$ moving with speed $v$ towards east strikes another particle of same mass moving with same speed $v$ towards north. After striking, the two particles fuse together. With what speed this new particle of mass $2\,m$ will move in north-east direction?

• A. $v$
• B. $\frac{v}{2}$
• C. $\frac{v}{\sqrt{2}}$
• D. $v\sqrt{2}$

Answer 1

Answer: (D)

$v\sqrt{2}$

Answer 2

From conservation of linear momentum $mv + mv =2 mv$
$\sin 135^{\circ}$
$2 m v=2 m v \times \frac{1}{\sqrt{2}}$
$v=\sqrt{2} v$