The primary responsibilities of human resources are: 1  C - Compensation. 2  H - Human resource development. 3  E - Employee and labor relations. 4  S - Safety and health. 5  S - Staff.
A new technique uses sound waves to levitate objects and move them in mid-air. Credit: Dimos Poulikakos View full size image. View full size image. Hold on to your wand, Harry Potter: Science has outdone even your best Leviosa! levitation spell.
Quick Answer. Sound waves travel fastest through a solid material. The second fastest medium is a liquid, and the slowest medium is a gas, because sound waves travel by vibrating molecules in a medium. In solids, these molecules are spaced closer together, causing sound to travel faster through it.