NAPT Fluid Mechanics and Hydraulics 1 — Questions and Answers
Question 1: Pascal's Law states that pressure applied to a confined fluid is transmitted:
- Only upward through the fluid
- Equally in all directions throughout the fluid (Correct answer)
- Only to the nearest surface
- Proportional to the fluid's viscosity
Correct answer: Equally in all directions throughout the fluid
Pascal's Law states that pressure applied to a confined, incompressible fluid is transmitted equally and undiminished in all directions throughout the fluid.
Question 2: According to Bernoulli's principle, as the velocity of a fluid increases, its pressure:
- Increases proportionally
- Remains constant
- Decreases (Correct answer)
- Doubles
Correct answer: Decreases
Bernoulli's principle states that in a flowing fluid, an increase in velocity corresponds to a decrease in static pressure, reflecting conservation of energy.
Question 3: The gauge pressure at the bottom of a column of water 10 meters deep (density = 1000 kg/m³, g = 9.8 m/s²) is approximately:
- 9,800 Pa
- 98,000 Pa (Correct answer)
- 980 Pa
- 0 Pa
Correct answer: 98,000 Pa
Gauge pressure P = ρgh = 1000 × 9.8 × 10 = 98,000 Pa; gauge pressure measures pressure above atmospheric.
Question 4: Archimedes' principle states that the buoyant force on a submerged object equals:
- The weight of the object
- The volume of the object times gravity
- The weight of the fluid displaced by the object (Correct answer)
- The surface area of the object times fluid pressure
Correct answer: The weight of the fluid displaced by the object
Archimedes' principle states that the buoyant force equals the weight of the fluid displaced by the object, which is why objects float when this force equals their own weight.
Question 5: The continuity equation for incompressible fluid flow states that:
- Pressure times velocity is constant
- Density times temperature is constant
- The product of cross-sectional area and flow velocity is constant (Correct answer)
- Volume flow rate increases with pipe diameter
Correct answer: The product of cross-sectional area and flow velocity is constant
The continuity equation (A₁V₁ = A₂V₂) requires that the volume flow rate is conserved, so a smaller cross-section forces the fluid to move faster.
Question 6: Viscosity in a fluid is a measure of its:
- Density relative to water
- Resistance to flow or internal friction (Correct answer)
- Ability to compress under pressure
- Surface tension at an interface
Correct answer: Resistance to flow or internal friction
Viscosity quantifies a fluid's resistance to deformation or flow; high-viscosity fluids like honey resist shear forces more than low-viscosity fluids like water.
Question 7: In a hydraulic lift system, a small piston with area 0.01 m² has a force of 100 N applied. What force is exerted by a large piston with area 0.5 m²?
- 2 N
- 5,000 N (Correct answer)
- 100 N
- 500 N
Correct answer: 5,000 N
By Pascal's Law, pressure is equal on both pistons: P = F₁/A₁ = 100/0.01 = 10,000 Pa; F₂ = P × A₂ = 10,000 × 0.5 = 5,000 N.
NAPT Fluid Mechanics and Hydraulics 1
Pascal's Law states that pressure applied to a confined fluid is transmitted: