🔬 Science & Engineering — Free Online Calculators & Tools

Speed is a scalar (magnitude only): distance/time. Velocity is a vector (magnitude + direction): displacement/time. A car driving at 60 km/h in a circle has constant speed but changing velocity (direction changes). In physics problems, direction matters for velocity, acceleration, and force calculations.

Use dimensional analysis (factor-label method): multiply by conversion fractions that equal 1. Example: 60 km/h to m/s: 60 × (1000m/1km) × (1h/3600s) = 60,000/3600 = 16.67 m/s. Always cancel units: km/h × m/km × h/s = m/s. Our unit converters handle common physics conversions automatically.

PV = nRT, where P = pressure (Pa), V = volume (m³), n = moles of gas, R = 8.314 J/(mol·K) (universal gas constant), T = temperature (Kelvin). Used to calculate any one variable when the others are known. Assumes ideal gas behaviour (no intermolecular forces, point particles) — accurate for most gases at moderate conditions.

pH = -log₁₀[H⁺], where [H⁺] is hydrogen ion concentration in mol/L. pH 7 = neutral (pure water at 25°C). pH < 7 = acidic (H⁺ > 10⁻⁷ mol/L). pH > 7 = basic/alkaline. Each pH unit = 10× change in H⁺: pH 5 is 10× more acidic than pH 6, 100× more than pH 7.

Mass (kg): measure of matter — constant everywhere in the universe. Weight (N = Newtons): gravitational force on that mass = mass × g. On Earth: g ≈ 9.81 m/s², so a 70 kg person weighs 70 × 9.81 = 686.7 N. On the Moon (g ≈ 1.62 m/s²): same mass but weight = 113.4 N. Weighing scales actually measure mass in everyday life.