What is the resultant of a and b if a = 3i 3j and b = 3i − 3j?

What are similarities and differences between refraction, reflection, diffraction and absorption?

The ratio of lift to drag l/d for a wing or airfoil is an important aerodynamic parameter, indeed, it is a direct measure of the aerodynamic efficiency of the wing. if a wing is pitched through a range of angle of attack, l/d first increases, then goes through a maximum, and then decreases. consider an infinite wing with an naca 2412 airfoil. estimate the maximum value of l/d. assume that the reynolds number is 9x10^6.

What is the measure of a change in an objects velocity?