Work (W) is said to be done, when a force (F) acts on the body and point of application of the force is displaced (s) in the direction of force.
Work done = force x displacement
W = F x s
ENERGY - The energy of the body is defined as its capacity to do workUnit of energy - Energy is measured in terms of work. Unit of energy is also joule. One joule of energy is required to do one joule of work
egaphone is a technology that is commonly used for announcements in public, it amplifies the voice of the speaker as loud as he wants.Megaphones, Horns and Loudspeakers: megaphones, horns (in cars, buses, etc.) and loudspeakers propagate sound in a particular direction. These instruments are specially designed with a conical opening in front of a small tube. Multiple reflections of sound from the conical part help in guiding the sound in a particular direction towards the audiences. These objects are used to address small gathering of people.
An echo is the phenomenon of repetition of sound of a source by reflection from an obstacle. To distinguish an echo from the original sound, the obstacle must be situated at a suitable distance from the source of sound. This depends upon the type of sound produced, which may be simple or articulate.