Question

Define work. How is work measured? When is work done by a force said to be negative? ​

Answer 1

The SI unit of work is joules (J). Work done is said to be negative, if the displacement of the given object occurs in the opposite direction (180°) of the applied force. ... The angle between the displacement and the frictional force is 180°. Thus the work done by the frictional force is negative

Answer 2

The SI unit of work is joules (J). Work done is said to be negative, if the displacement of the given object occurs in the opposite direction (180°) of the applied force. ... The angle between the displacement and the frictional force is 180°. Thus the work done by the frictional force is negative