Question

A child carries a 3N book at a constant velocity 4 meters across a horizontal floor. What is the net work done?

Answer 1

Note that 4  m (meters) has the units of distance, not velocity.

By definition,
Work = Force x Distance
Therefore if a 3 N book is carried over a distance of 4 m, the work done is
3 *3 4 = 12 J

Answer:  12 J