Let's say you jump on a trampoline. Consider the time when you land on the mat and the trampoline slows you down. What can you say about your potential energy? the gravitational potential energy will decrease the elastic potential energy will decrease the gravitational potential energy will not change the elastic potential energy will increase the gravitational potential energy will not change for conservation of mechanical energy, both forms of PE should be considered for conservation of mechanical energy, only the gravitational PE should be considered