A body constrained to move along the z-axis of a coordinate system is subject to a constant force F given by
Where 
are unit vectors along the x-, y- and z-axis of the system respectively. What is the work done by this force in moving the body a distance of 4 m along the z-axis?
Given,
Force, 
N
Displacement, 
m
Work done, W = 
So, W = 
⇒ W = 3×4
⇒ W = 12 J
11