Agricultural and Biological Engineering PE

Always identify whether friction factor f is given or must be calculated using Reynolds number and relative roughness. On PE exam, f is often provided. Watch units carefully - diameter and length must be in same units. Gravity constant differs between SI and English units.

Darcy's Law appears frequently in environmental and geotechnical PE problems. Remember it applies only to laminar flow (typical in most groundwater situations). Watch units carefully - hydraulic conductivity values span many orders of magnitude. The hydraulic gradient (Δh/L) is dimensionless.

First-order kinetics appears frequently in environmental and water treatment problems. Remember that the half-life is t₁/₂ = ln(2)/k = 0.693/k. The equation assumes constant temperature and environmental conditions. Watch for unit consistency between rate constant and time.

Hooke's Law is fundamental to structural analysis problems. Remember it only applies within the elastic limit - watch for yield stress values in problems. Often appears combined with deflection formulas or in composite material questions. Always check units carefully as modulus values are typically given in GPa or ksi.

On the PE exam, Manning's equation appears frequently in water resources problems. CRITICAL: Use k=1.49 for English units (ft) and k=1 for SI units (m). Always calculate hydraulic radius first (R = A/P). Slope S is dimensionless (rise/run). Common exam tricks include providing channel dimensions requiring geometric calculations for area and wetted perimeter.