Question

what is the potential energy of a rock that weights 100 newtons that is sitting on top of a hill 300 meters high

Answer 1

The potential energy is the work it took to move the rock to the top of the hill.

                 Work  =  (force)  x  (distance)
 
                            =  (100 newtons) x (300 meters)

                           =      30,000  newton-meters

                           =      30,000 joules  .