Which of the following is not an assumption for an ideal fluid flow for which Bernoulli's principle is valid?

Two light balls are suspended as shown in the figure. When a stream of air passes through the space between them,the distance between the balls will

Two immiscible liquids are filled in a conical flask as shown in the figure. The cross-sectional area is shown. $A$ small hole of area $a$ is made in the lower end of the cone. Find the speed of liquid flow from the hole.

$A$ train with cross-sectional area $S_t$ is moving with speed $v_t$ inside a long tunnel of cross-sectional area $S_0$ $(S_0 = 4S_t)$. Assume that almost all the air (density $\rho$) in front of the train flows back between its sides and the walls of the tunnel. Also,the air flow with respect to the train is steady and laminar. Take the ambient pressure and that inside the train to be $p_0$. If the pressure in the region between the sides of the train and the tunnel walls is $p$,then $p_0 - p = \frac{7}{2N} \rho v_t^2$. The value of $N$ is. . . . .

$A$ liquid is flowing in a horizontal pipe of non-uniform cross-section. Which of the following quantities may remain unchanged with respect to time?

In the case of a fluid,Bernoulli's theorem expresses the application of the principle of conservation of :