Mechanical Aptitude Fluid Dynamics Principles Flashcards

Oil with a specific gravity of 0.85 is resting on top of water. What does this tell you about the oil?

Answer: Oil is less dense than water and floats

Specific gravity less than 1.0 means the fluid is less dense than water, so oil floats on the water surface.

A Venturi meter is used to measure:

Answer: Flow rate through a pipe

A Venturi meter measures flow rate by detecting the pressure difference between a wide section and a narrow throat section of a pipe.

At what point in a piping system is cavitation most likely to occur?

Answer: Where pressure drops below the fluid's vapor pressure

Cavitation occurs when local pressure falls below the vapor pressure of the fluid, causing vapor bubbles to form.

A tank has a hole near its base. As the water level in the tank drops, what happens to the velocity of water exiting the hole?

Answer: Velocity decreases

By Torricelli's theorem, exit velocity = √(2gh), so as height h decreases, exit velocity decreases.

In a hydraulic system, which of the following best describes Pascal's Law?

Answer: Pressure applied to a confined fluid is transmitted equally in all directions

Pascal's Law states that pressure changes applied to an enclosed fluid are transmitted undiminished throughout the entire fluid.

A pump rated at 2 HP is used to move water through a pipe. If friction losses consume 30% of the pump's power, how much power is actually delivered to the water?

Answer: 1.4 HP

Power delivered to water = 2 HP × (1 − 0.30) = 2 × 0.70 = 1.4 HP.

Which statement correctly describes the difference between gauge pressure and absolute pressure?

Answer: Absolute pressure equals gauge pressure plus atmospheric pressure

Absolute pressure = gauge pressure + atmospheric pressure (approximately 14.7 psi at sea level).