Question

1.      Which of the following must be satisfied by the flow of any fluid, real or ideal?

I. Newton's second law of motion

II. the continuity equation

III. the requirement of a uniform velocity distribution

IV. Newton's law of viscosity

V. the principle of conservation of energy

a)      I, II, and III

b)      I, II, and IV

c)      I, II, III, and N

d)      I, II, and V

e)      I, II, N, and V

Answer 1

Theory: it is more of a qualitiative question which wants us to differentiate between universal laws and the laws which are specific to some assumptions or conditions.

Solution:

1. Newton's second law of motionstates that acceleration of any object is dependent upon mass and the forces acting on it. There is no assumption in this law. This law is an universal law. So it is indpendent on any fluid/real or ideal nature.

2. Continuity equation: It is basically the conservation of mass. We all know that mass can never be created nor be destroyed. Mass is universally conserved so it is also indepndent on fluid/real or ideal nature of fluid.

3.Uniform velocity distribution: this is true only for laminar flow where reynolds number is less than 3000. For turbulent flow velocity ditribution may not be uniform so this law depends upon condition of fluid.

4. Newtonian's law of viscocity: this law is valid only for those fluid which are newtonial fluid. For non-newtonian fluid this law is not applicable so this law is also dependent upon type of fluid.

5. Conservation of energy: Energy can neither be created nor be destroyed. It can only be converted from one form into other. Thus this is an universal law and is indepndent on type of fluid or real/ideal nature of fluid.

Thus Except I, II,V are the only satisfied statements. Correct option should be (d)