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.
Full Answer. Sound has the ability to travel through gases, liquids and solids. How Stuff Works sates that the speed of any sound wave is highly dependent on the medium through which it travels. The speed of sound is greater when it travels through solids. It travels more slowly when it goes through liquids and gases.