Question 46 in the morning session of the 2014 professional knowledge exam: the conservation laws governing fluid flow
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I saw that the answers given online are conservation of mass, conservation of energy, and conservation of momentum. Conservation of mass and conservation of energy are not controversial, but as for conservation of momentum, can anyone explain why it holds true?
The law of conservation of momentum is primarily applied in the following three situations: (1) the net force acting on a system is zero. (2) The external force acting on the system is much smaller than the interaction forces (internal forces). To the point where the influence of external forces can be ignored. (3) The system as a whole does not satisfy the law of conservation of momentum, but in a particular direction, if the system is subject to no external forces, or if the external forces acting on it are much smaller than the internal forces, then the component of momentum of the system along that direction is conserved