Definition of Work in physics

 Work: When force is applied on a body and body covers some distance is called workdone.

 It is scalar quantity. Its S.I unit is joule or N.m or Kg m² /s².

 W=F.D cos theta . 

 At zero degree work is positive. At 180° degree

 work is negative. 

 At 90 degree work is zero. 

 When a body moves in a circular path, the workdone by the centripetal force is zero, 

because centripetal force is always at right angles to the direction to the direction in 

which the body moves. 

 Upward work is negative due to gravity (in opposite direction of gravity) 

 Downward work is positive towards gravitational force. 

 If a person walks along a level surface while carrying a box, no work is done because 

box has no force to the direction of the person.