What happened to sound if the frequency of the vibrations increases

Gunpowder residue is most likely to show up where on a shooters hands

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.

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?