How is 'work' defined in physics?

Answer 1

'Work' as defined in physics is the displacement of a material object from its original position by the application of a force in the direction of that force. In other words, in order for work to be performed in the strict physical sense, the body must move through space in the direction of the force. No work is performed if the object does not move in a particular direction through space. Movement through space in a definite direction therefore is necessary in the performance of work in the strict physical sense. While the body is moving through space, energy is being transferred. So a secondary definition of 'work' is the transfer of energy through the motion of a body. This idea parallels the ordinary definition of the word 'work' in the sense of 'activity for a purpose that requires physical or mental exertion'. Not all activity is work even in the general sense. The activity must have a goal or purpose, that is a 'direction' in order for it to be considered 'work'. Play therefore cannot be considered 'work' since it has no definite direction or purpose other than that of amusement or recreation. Nevertheless, play is an activity since there is some movement of the body or some transfer of energy. And sleep cannot be considered 'work' since there is no movement of the body at all although the body continues to work internally through the repair and rejuvenation of cells and tissues and also through the circulation of blood by the contraction and relaxation of the heart. So 'work' therefore is defined as the transfer of energy by the motion or activity of a body toward a particular direction, purpose, or goal.