Bennett Mechanical Test Fluid Mechanics and Hydraulics 3 — Questions and Answers
Question 1: Which statement best describes Bernoulli's principle?
- Faster-moving fluid exerts lower pressure (Correct answer)
- Faster-moving fluid exerts higher pressure
- Pressure is unrelated to fluid speed
- Fluid speed depends only on temperature
Correct answer: Faster-moving fluid exerts lower pressure
Bernoulli's principle states that as fluid velocity increases, its pressure decreases.
Question 2: When water flows through a pipe that narrows, the water's speed:
- Decreases
- Increases (Correct answer)
- Stays the same
- Drops to zero
Correct answer: Increases
By continuity, the same volume passing through a smaller area must move faster.
Question 3: As water flows through a narrowing section of pipe, the pressure in that narrow section:
- Increases
- Decreases (Correct answer)
- Doubles exactly
- Is unaffected
Correct answer: Decreases
Faster flow in the narrow section lowers the pressure per Bernoulli's principle.
Question 4: The continuity equation for fluids states that, for a given pipe, the product of which two quantities stays constant?
- Pressure and temperature
- Cross-sectional area and velocity (Correct answer)
- Density and color
- Length and width
Correct answer: Cross-sectional area and velocity
Area × velocity is constant, so flow rate is conserved along the pipe.
Question 5: Why does the roof of a house sometimes lift off during high winds?
- Wind adds weight to the roof
- Fast wind over the roof lowers pressure above it (Correct answer)
- Air inside the house cools rapidly
- The roof absorbs water
Correct answer: Fast wind over the roof lowers pressure above it
Fast air over the roof creates lower pressure above, so higher inside pressure pushes it up.
Question 6: A garden hose sprays water farther when you cover part of the opening with your thumb because:
- The water becomes lighter
- Reducing the area increases the exit velocity (Correct answer)
- Pressure inside the hose drops
- The water heats up
Correct answer: Reducing the area increases the exit velocity
Shrinking the opening forces the same flow through a smaller area, raising exit speed.
Question 7: An atomizer or spray bottle works because air moving quickly past a tube:
- Heats the liquid
- Creates low pressure that draws liquid up (Correct answer)
- Increases the liquid's density
- Freezes the nozzle
Correct answer: Creates low pressure that draws liquid up
Fast-moving air lowers pressure at the tube top, so atmospheric pressure pushes liquid up.
Bennett Mechanical Test Fluid Mechanics and Hydraulics 3
Which statement best describes Bernoulli's principle?