Question

A car of mass 10 metric ton rolls at $2m{s}^{-1}$ along a level track and collides with a loaded car of mass 20 metric ton, standing at rest. If the cars couple together, the common speed after collision is

• A. $1m{s}^{-1}$
• B. $0.67m{s}^{-1}$
• C. $0.5m{s}^{-1}$
• D. $0.3m{s}^{-1}$

Answer 1

The correct option is B $0.67m{s}^{-1}$

Using linear momentum conservation
$10\times 2+20\times \left(0\right)=30\times v$
$\Rightarrow v=0.67m/s$