Mechanical Aptitude Mechanical Aptitude Fluid Dynamics Principles Questions and Answers 2 — Questions and Answers
Question 1: A pipe narrows from a 4-inch diameter to a 2-inch diameter. If water flows at 2 ft/s in the wider section, what is the approximate velocity in the narrower section?
- 4 ft/s
- 6 ft/s
- 8 ft/s (Correct answer)
- 16 ft/s
Correct answer: 8 ft/s
By the continuity equation, reducing the diameter by half reduces the area by a factor of four, so the velocity increases four times from 2 ft/s to 8 ft/s.
Question 2: Which principle explains why a shower curtain gets pulled inward when the water is running?
- Pascal's principle
- Bernoulli's principle (Correct answer)
- Archimedes' principle
- Boyle's law
Correct answer: Bernoulli's principle
The fast-moving air created by the shower reduces pressure on the inside of the curtain, and higher outside pressure pushes it inward, which is explained by Bernoulli's principle.
Question 3: A hydraulic system has a small piston with an area of 5 sq in and a large piston with an area of 50 sq in. If 20 lbs of force is applied to the small piston, what force is exerted by the large piston?
- 20 lbs
- 100 lbs
- 200 lbs (Correct answer)
- 1,000 lbs
Correct answer: 200 lbs
By Pascal's principle, the force is multiplied by the ratio of piston areas: 20 lbs x (50/5) = 200 lbs.
Question 4: What happens to the flow rate in a pipe if the fluid viscosity doubles while all other factors remain constant?
- Flow rate doubles
- Flow rate stays the same
- Flow rate is reduced by half (Correct answer)
- Flow rate is reduced to one-quarter
Correct answer: Flow rate is reduced by half
According to the Hagen-Poiseuille equation, flow rate is inversely proportional to viscosity, so doubling viscosity halves the flow rate.
Question 5: A tank has two outlet holes at different heights. Which statement is correct about the water streams?
- The higher hole produces a faster stream
- The lower hole produces a faster stream (Correct answer)
- Both holes produce streams at the same speed
- Stream speed depends only on hole size
Correct answer: The lower hole produces a faster stream
By Torricelli's theorem, the exit velocity depends on the depth of fluid above the hole, so the lower hole has greater pressure and produces a faster stream.
Question 6: In a venturi meter, what happens at the narrowest section of the tube?
- Both pressure and velocity increase
- Pressure increases and velocity decreases
- Pressure decreases and velocity increases (Correct answer)
- Both pressure and velocity decrease
Correct answer: Pressure decreases and velocity increases
As the cross-section narrows, fluid velocity increases and pressure decreases according to Bernoulli's principle.
Mechanical Aptitude Mechanical Aptitude Fluid Dynamics Principles Questions and Answers 2
A pipe narrows from a 4-inch diameter to a 2-inch diameter.
If water flows at 2 ft/s in the wider section, what is the approximate velocity in the narrower section?