Engineering Sciences Flashcards

What is the principle of virtual work?

Answer: A system in equilibrium does zero virtual work for any virtual displacement

The principle states that for a system in static equilibrium, the total virtual work done by all forces during any compatible virtual displacement is zero. It is powerful for solving indeterminate structures.

Fourier's law of heat conduction states that heat flux is proportional to:

Answer: The negative temperature gradient

Fourier's law: q = -k(dT/dx), where the negative sign indicates heat flows from high to low temperature. The thermal conductivity k depends on the material.

The natural frequency of a single degree of freedom system is:

Answer: ωn = √(k/m)

The natural frequency ωn = √(k/m) where k is stiffness and m is mass. This determines the frequency at which the system oscillates freely and is critical for avoiding resonance.

In materials science, what is creep?

Answer: Time-dependent deformation under constant stress at elevated temperature

Creep is the slow, progressive plastic deformation of a material under constant stress over time, especially at temperatures above ~0.4 of the melting point. This is particularly relevant in Saudi Arabia's hot climate.

The drag coefficient of a sphere in laminar flow is given by Stokes' law as:

Answer: CD = 24/Re

For very low Reynolds numbers (Re < 1), Stokes' law gives CD = 24/Re for a sphere. This applies to slow-moving particles, sediment settling, and dust particle analysis.

What is the Stefan-Boltzmann law?

Answer: The total radiant heat energy emitted is proportional to the fourth power of absolute temperature

The Stefan-Boltzmann law states q = εσT⁴, where σ = 5.67×10⁻⁸ W/m²K⁴. This is critical for solar radiation calculations in Saudi Arabia's intense desert environment.