The Force of Drag equation, Fdrag= ½⋅(ρ⋅A⋅Cd⋅v²) , Forces on motion in flight. calculates the resisting force of drag on an object flowing through a medium (e.g. air).
INSTRUCTIONS: Choose your preferred units and enter the following:
Force of Drag (Fdrag) The force of drag or air-resistance is returned in newtons. However, this can be automatically converted to other force units via the pull-down menu.
The default units are Pa - kg/m3, Cd - N/A, A - m2, V - m/s. However, vCalc provides automatic unit conversions in many cases.
The graphic shows some common drag coefficients based on the shape of the object. Note, that there are other factors besides shape that can effect drag.
Graphics courtesy of Wikipedia (Drag coefficient)
The density of air, ρ (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere. Air density, like air pressure, decreases with increasing altitude. It also changes with variation in temperature or humidity. At sea level and at 15 °C, air has a density of approximately 1.225 kg/m3 (0.001225 g/cm3, 0.0023769 slug/ft3, 0.0765/ft3) according to ISA (International Standard Atmosphere).