Question

A body of mass 2kg is moving with velocity 10 m/s towards east. Another body of same mass and same velocity moving towards north collides with former and coalsces and moves towards north-east. Its velocity is

• A. 10 m/s
• B. 5 m/s
• C. 2.5 m/s
• D. $5\sqrt{2}m/s$

Answer 1

Answer: (D)

$5\sqrt{2}m/s$

Answer 2

Initial momentum =

$| \vec { P } | = \sqrt { 2 } m v$

Final momentum = $2 m \times V$

By the law of conservation of momentum

$2 m \times V = \sqrt { 2 } m v$⇒ $V = \frac { v } { \sqrt { 2 } }$

In the problem $v = 10 \mathrm {~m} / \mathrm { s }$ (given)

∴ $V = \frac { 10 } { \sqrt { 2 } } = 5 \sqrt { 2 } \mathrm {~m} / \mathrm { s }$