Echo, a repeated sound. The term is usually used to refer to sound that is reflected from a surface and returned to its source after a noticeable delay.
Torsion, the stress produced in a body when it is twisted. The twist in the body is produced by torque. See more »
Ultraviolet Radiation, electromagnetic radiation with wavelengths between those of visible violet light and those of X rays. See more »
Vacuum, a space in which there is no matter. In a strict sense, there is no such thing as a vacuum—even the virtually empty regions of the universe between the galaxies contain some matter. See more »
Work, in physics, the movement of a body by a force acting against a resistance. Work is performed when a person lifts a weight, since the person applies a force to move the weight upward. See more »
X Rays, electromagnetic radiation similar to that of visible light, but of much shorter wavelength. See more »