*Problem 1: A particle of mass m is displaced from a position P _{1} to P_{2} with position vectors and by a force .*

*Find the work done by the force.*** Solution: **If the displacement of the particle is , the work done W by the given force is equal to W = F

^{→}.S

^{→}, when F

^{→}is a constant force.

W = F^{→}.S^{→} …(1)

where

…(2)

and

…(3)

Using (1), (2) and (3)

Þ W = (c-a)b + (a-b)c + (b-c)a

Þ W = bc – ab + ac – bc + ab – ac = 0

Net work done by the force for the given displacement is zero.