A body constrained to move along the z-axis of a coordinate system is subject to a constant forceF   given by F=-i^+2j^+3k^N

Where i^,j^,k^ 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?

Force exerted on the body, F=-i^+2j^+3k^N

Displacement, s = 4k^m

Work done, W=F.s
=-i^+2j^+3k^.4k^
=0+0+3x4=12J

Hence, 12 J of work is done by the force on the body.