Mechanical Aptitude Fluid Dynamics Principles Flashcards
7 cards from real MECHANICAL APTITUDE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Mechanical Aptitude Fluid Dynamics Principles flashcards as text
A pipe narrows from 4 inches in diameter to 2 inches in diameter. How does the fluid velocity change at the narrower section?
Answer: It quadruples
By the continuity equation, when diameter halves the cross-sectional area quarters, so velocity must quadruple to maintain the same flow rate.
Which factor does NOT directly affect the buoyant force acting on a submerged object?
Answer: Material composition of the object
Buoyant force equals the weight of displaced fluid, which depends on the object's volume and fluid density, not the object's material composition.
Water flows through a horizontal pipe. At a section where the pipe widens, what happens to the pressure?
Answer: Pressure increases
According to Bernoulli's principle, where velocity decreases (wider pipe) pressure increases, since total energy is conserved.
A hydraulic jack uses a small piston of area 2 in² and a large piston of area 20 in². If you apply 50 lb of force on the small piston, what force is produced at the large piston?
Answer: 500 lb
Pascal's law states pressure is equal throughout: F_out = F_in × (A_out/A_in) = 50 × (20/2) = 500 lb.
What is the primary reason turbulent flow creates more resistance than laminar flow in a pipe?
Answer: Turbulent flow creates chaotic mixing that dissipates more energy
Turbulent flow causes random, chaotic motion and eddies that convert kinetic energy into heat, significantly increasing energy loss and resistance.
A fluid with higher viscosity will generally have which of the following characteristics compared to a low-viscosity fluid?
Answer: It has a lower Reynolds number at the same velocity
Reynolds number = ρvD/μ, so higher viscosity (μ) produces a lower Reynolds number, making laminar flow more likely.
In a closed hydraulic system, if a valve is suddenly shut, the resulting pressure surge is called:
Answer: Water hammer
Water hammer is the pressure wave created when flowing fluid is suddenly stopped, often heard as a banging in pipes.