Net (Science )

Work
Definition: The work done by an agent exerting a constant force ( F ) and causing a displacement ( d ) equals the magnitude of the displacement, s, times the component of along the direction of the work done by is:

W = s .F.cos0.

Mathematically, work can be expressed by the following equation.


where F = force, d = displacement, and the angle (theta) is defined as the angle between the force and the displacement vector. Perhaps the most difficult aspect of the above equation is the angle "theta." The angle is not just any 'ole angle, but rather a very specific angle. The angle measure is defined as the angle between the force and the displacement. To gather an idea of its meaning, consider the following three scenarios.Scenario A: A force acts rightward upon an object as it is displaced rightward. In such an instance, the force vector and the displacement vector are in the same direction. Thus, the angle between F and d is 0 degrees.
Scenario B: A force acts leftward upon an object which is displaced rightward. In such an instance, the force vector and the displacement vector are in the opposite direction. Thus, the angle between F and d is 180 degrees.
Scenario C: A force acts upward upon an object as it is displaced rightward. In such an instance, the force vector and the displacement vector are at right angles to each other. Thus, the angle between F and d is 90 degrees







Scenario A: A force acts rightward upon an object as it is displaced rightward. In such an instance, the force vector and the displacement vector are in the same direction. Thus, the angle between F and d is 0 degrees.
Scenario B: A force acts leftward upon an object which is displaced rightward. In such an instance, the force vector and the displacement vector are in the opposite direction. Thus, the angle between F and d is 180 degrees.
Scenario C: A force acts upward upon an object as it is displaced rightward. In such an instance, the force vector and the displacement vector are at right angles to each other. Thus, the angle between F and d is 90 degrees.






Note:

If d = 0 W = 0. (ie: no work is done when holding a heavy box, or pushing against a wall).
W = 0 if (ie: no work is done by carrying a bucket of water horizontally).
The sign of W depends on the direction of relative to : W > 0 when component of along is in the same direction as , and W < 0 when it is in the opposite direction. This sign is given automatically if we write as the angle between and and write W = Fscos .
If acts along the direction of then W = Fs , since cos = cos 0 = 1.
Work is a scalar.
The SI units of work are Joules (J) (1 Joule = 1 Newton meter). In cgs units: 1 erg = 1 dyne cm