The third and fourth stages of a rocket are coastin in space

The third and fourth stages of a rocket are coastin; in space with a velocity of 18 000 km/h when a small explosive charge between the stages separate them. Immediately after separation the fourth stag has increased its velocity to v_4 = 18 060 km/h. What is the corresponding velocity v_3 of the third stage At separation the third and fourth stages hav masses of 400 and 200 kg, respectively.

Solution

>> As, Momentum will be conserved

>> So, Initial Momentum = Final Momentum

=> M*Vi = m3*V3 + m4*V4

M = Total Mass = m3 + m4 = 400 + 200 = 600 Kg

Vi = 18000 km/h

v3 = 18060 km/hr

v4 = ?

So, putting all

=> 600*18000 = 400*V3 + 200*18060

=> V3 = 17970 km/hr ......ANSWER.......