1. The problem statement, all variables and given/known data I know that standard formula is, FD = 1/2 CD *ApV^2 FD = Drag Force. SI: N CD = Drag Coefficient. SI: Dimensionless (Typical Values) A = Coss-sectional Area perpendicular to the flow. SI: m2 r = Density of the medium. SI: kg/m3 v = Velocity of the body relative to the medium. SI: m/s But our prof also said theres another formula for drag force, FD = 1/4 AV^2 (Its is not supposed to be equal but approximately) So the question is when is the equation above false, whats the error in the equation that makes it approximate. 2. Relevant equations FD = 1/4 AV^2 FD = 1/2 CD *ApV^2 3. The attempt at a solution I searched everywhere on wikipedia and NASA site and no luck and I dont know integration yet so can't follow the complicated math. Please anyone can help me.