Fluid Mechanics - Study Mode

[#426] What is the force required (in Newtons) to hold a spherical balloon stationary in water at a depth of H from the air-water iterface? The balloon is of radius 0.1 m and is filled with air.
Correct Answer

(A) $$frac{{4pi { ext{g}}}}{3}$$

[#427] With increase in molecular weight of the gas, the head developed by a centrifugal compressor will
Correct Answer

(A) Decrease

Explanation

Solution: The head developed by a centrifugal compressor is dependent on the kinetic energy imparted to the gas. The kinetic energy is directly related to the velocity of the gas molecules. With an increase in molecular weight of the gas, the average velocity of the gas molecules decreases due to higher mass. This results in a decrease in kinetic energy and consequently, a decrease in the head developed by the centrifugal compressor. Hence, the correct answer is Option A: Decrease .

[#428] Priming of a centrifugal pump is done to
Correct Answer

(B) Develop effective pressure rise by the pump

Explanation

Solution: The correct answer is Option B: Develop effective pressure rise by the pump . Here's why: Priming a centrifugal pump means filling the pump casing and suction pipe completely with the liquid to be pumped *before* starting the pump. Why is this important? If the pump casing is filled with air or gas, the impeller (the rotating part) will mostly just churn the air. Centrifugal pumps need to be filled with liquid to work correctly. Let's look at the other options: * Option A: Increase the mass flow rate of fluid: Priming doesn't directly increase the flow rate once the pump is running, but is a prerequisite for pumping to commence. * Option C: Avoid chances of separation inside the impeller: While cavitation (separation) *can* be worsened by improper priming, the *primary* reason for priming is to create an initial pressure head. * Option D: None of these: This is incorrect since priming does have a specific purpose. Therefore, the main reason for priming is to remove air and create a liquid-filled environment so the impeller can effectively develop pressure and begin pumping.

[#429] Pressure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as
Correct Answer

(D) V 2

[#430] __________ pump is the most suitable device for discharging a liquid against a pressure of ≥ 1500 kgf/cm 2 .
Correct Answer

(C) Plunger