A body of mass m moving with velocity v collides head on with another body of mass $2m$ which is initially at rest. The ratio of K.E of colliding body before and after collision will be

Question

$$(a)\;1:1 \quad (b)\;2:1\quad (c)\; 4:1 \quad (d)\;9:1$$

Comments

Being head on elastic collision how the mass will add