Question

Is momentum conserved in variable mass system?

• A. yes
• B. never
• C. in specified cases
• D. cannot say

Answer 1

Answer: (C)

in specified cases

Momentum is conserved in a variable mass system if and only if external forces acting on the system adds up to 0, by Newton's second law.

If velocity is constant, momentum will be non zero since $\frac{dM}{dt}\ne 0$. If external forces are zero, velocity of system will varry according to the mass for net momentum to remain constant. Hence momentum is not always conserved in variable mass system.