Mechanical Properties of Fluids MCQs for NEET — Physics Questions with Answers

The NCERT text states, 'No two streamlines can cross, for if they do, an oncoming fluid particle can go either one way or the other and the flow would not be steady. Hence, in steady flow, the map of flow is stationary in time.' This precisely defines steady flow.

The NCERT text explicitly states 'Av gives the volume flux or flow rate and remains constant throughout the pipe of flow.'

The text mentions, 'Steady flow is achieved at low flow speeds. Beyond a limiting value, called critical speed, this flow loses steadiness and becomes turbulent.'

From the equation of continuity, as the area decreases, the velocity increases. An increase in velocity over time implies acceleration. The text states, 'From (Fig 9.7b) it is clear that $A_R > A_Q$ or $v_R < v_Q$, the fluid is accelerated while passing from R to Q'.

The NCERT text specifies that 'For flow of incompressible fluids $\rho_P = \rho_R = \rho_Q$' and then states 'Equation (9.9) reduces to $A_P v_P = A_R v_R = A_Q v_Q$ (9.10) which is called the equation of continuity and it is a statement of conservation of mass in flow of incompressible fluids.'

The definition of an incompressible fluid implies that its density remains constant, regardless of changes in pressure or flow characteristics. The text states, 'For flow of incompressible fluids $\rho_P = \rho_R = \rho_Q$'.

A venturi-meter measures flow rate via pressure difference, derived from Bernoulli's equation.

Bubble has two surfaces: $W = T\times 2(4\pi r^2) = 0.03\times 8\pi\times (0.02)^2 \approx 3.01\times 10^{-4}\ \text{J}$.

$F = T \cdot 2\pi r = 0.07 \cdot 2\pi \cdot 0.045 \approx 19.8$ mN.

Balancing the Laplace pressure of the curved surface, $S\,\dfrac{d^2y}{dx^2} = \rho g\,y$ for small slopes, i.e. $\dfrac{d^2y}{dx^2} = \dfrac{\rho g}{S}\,y$.