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

A body of mass m moving with velocity v collides head on with another

1.	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
Answer» `1:1` `2:1` `4:1` `9:1` Solution :KE of COLLIDING BODIES before collision ` = 1/2 mv^3` After collision the MASS = m + 2m = 3m VELOCITY becomes ` V. =( (m_1 - m_2)/(m_1 + m_2) )v = (mv)/(3m)= v/3` KE AFTERCOLLISION ` = 1/2 m ( V/3)^2 = 1/9 (1/2 mv^2) ` ` (KE_("before"))/(KE_("after")) = (1/2 mv^2)/(1/9 (1/2 mv^2) ) = 9 : 1`