vec P_1=m_1*vec v_1" momentum of " m_1" before collision"
vec P_2=m_2*v_2" momentum of " m_2 " before collision"
vec Sigma P_b=vec P_1+vec P_2" total momentum before collision"
Sigma vec P_b=m_1*vec v_1+m_2*vec v_2
Sigma vec P_b=3.16+1*0=48 " "kg*m/s
"post collision velocities :"
vec v_1^'=(2*Sigma vec P_b)/(m_1+m_2)-vec v_1
vec v_1^'=(2*48)/(3+1)-16
vec v_1^'=96/4-16
vec v_1^'=24-16=8" "m/s
vec v_2^'=(2*Sigma vec P_b)/(m_1+m_2)-vec v_2
vec v_2^'=(2*48)/(3+1)-0
vec v_2^'=96/4
vec v_2^'=24" "m/s