Cindy pushes a bookshelf with all her strength (50N to the right) and it doesn't move a single inch! The bookshelf weighs 200N. How much work did Cindy do on the bookshelf?

0J, hence no work was done.

Explanation:

Step one:

given data

Applied force F= 50N

The bookshelf weighs 200N

Distance moved= 0 m

Going by the definition of work done "it is the application of force F along a distance"

Now from the scenario, yes Cindy applied a force even all her strength worth 50N, but the shelf did not even move an inch, hence no work was done, because

Work- done= Force* distance

Work- done= 50*0

Work done= 0J

see earlier answer