Missing question: "how much work is done by the teacher?" (found on internet)
Solution:
The work done to move the desk across the floor is equal to
[tex]W=Fd[/tex]
where F is the horizontal force applied to move the desk, and d is the distance covered by the desk. If we use F=20 N and d=5 m, we find the work done:
[tex]W=Fd=(20 N)(5 m)=100 J[/tex]
