Wind Resistance & Coefficients of Drag Drag is the force that resists an object moving through a fluid (air, water, anything). It’s governed by one of the most important equations in fluid mechanics: Fd = ½ρv²CdA Breaking It Down ρ (rho) — fluid density (air at sea level ≈ 0.00238 slug/ft³ or 1.225 kg/m³) v² … Read more
Why You Can Drill a Big Hole in an I-Beam Web It seems counterintuitive: you can cut a large hole in the middle of a steel beam’s web and barely reduce its load-carrying capacity. But once you understand where stress lives in a beam, it makes perfect sense. Where Bending Stress Lives When a beam … Read more
Modulus of Elasticity — Why Stiffness ≠ Strength Here’s a fact that surprises many engineers early in their career: 36 ksi yield steel and 36 ksi yield aluminum have the same strength — but the steel is 3× stiffer. Strength and stiffness are completely independent properties, and confusing them leads to bad designs. What Is … Read more
Pressure in Engineering — And Why It Gets Confusing Pressure seems simple: force per unit area. But between psi, bar, atm, Pascals, inches of mercury, feet of water head, and absolute vs gauge — it’s one of the most unit-confused concepts in engineering. The Basics P = F / A 1 psi = 1 pound … Read more
Stress — Compressive, Tensile, and Shear Stress is the internal force per unit area inside a material when external forces are applied. It looks like pressure (same units — psi, MPa), but it describes what’s happening inside the material, not on its surface. The Three Types σ = F / A Tensile Stress (pulling apart) … Read more
Moment of Inertia — Why a 2×6 on Edge is 13× Stiffer If stress tells you whether something will break, moment of inertia tells you whether it will bend. It’s the single most important concept in structural design, and it explains why beams are shaped the way they are. The Formula That Matters For a … Read more
Ohm’s Law: V = IR Ohm’s Law is to electrical engineering what F = ma is to mechanical. Three variables, one equation, and an enormous amount of practical power. What It Means V — Voltage (volts, V) — the “pressure” pushing electrons through a circuit I — Current (amps, A) — the flow rate of … Read more
Newton’s Second Law: F = ma If there’s one equation that defines mechanical engineering, it’s F = ma. Force equals mass times acceleration. It sounds simple — and it is — but its implications reach into every corner of engineering, from sizing a motor to designing a bridge. What It Means A force is what … Read more