In flight mechanics, the “resultant velocity at the propeller tip” refers to the total velocity experienced by the air at the outermost portion of the propeller blade. It is the vector sum of the freestream velocity (Vinfinite) and the tangential velocity due to the rotational motion of the propeller (Vt).
Vrtip = (Vinfinite^2 + 2 * π * n * r^2)
Vrtip = Tangential velocity at the propeller tip (velocity in meters per second or feet per second). Vinfinite = Freestream velocity or the velocity of the aircraft through the air (velocity in meters per second or feet per second). n = Rotational speed of the propeller (in revolutions per unit of time). r = Distance from the propeller axis to the tip of the blade (radius of the propeller blade, typically in meters or feet).