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.
Sound waves travel in. air at a speed of approximately 344 meters/second, while. electromagnetic waves travel at the speed of light. (300,000,000 meters/second). While mechanical waves need. something to move in e.g., air or water, electromagnetic waves. can travel in a vacuum. Another important characteristic of.