okay, if a bulldozer pushed a large boulder resting on the edge of a cliff deep into a pond, when the bulldozer pushed it off, what kind of energy did it use ? A. potential energy in the boulder was transformed into kinetic energyB. kinetic energy in the boulder was transformed into potential energyC. new kinetic energy was created by the boulderD. new potential energy was created by the boulder
the answer is A. when anything is at rest it has potential energy, but when it starts moving this changes to kinetic. C and D are wrong because energy can not be created or destroyed just transferred.
A is the answer. C and D don't make sense because you can't create energy. Kinetic, for example, can be like rolling down a hill--gravity pulls it. Potential energy means it's not in motion yet, but potentially can have this much energy.
First, you cannot create energy, so answers C and D are obviously out. Potential energy means not being used or standing still, and Kinetic Energey means moving. The standing still boulder was FULL of potential energy, the fact that it wasn't moving was because there was a balance at that moment between gravity and the boulder on the cliff. The force from the bulldozer transformed the boulder's potential energy into kinetic energy (the boulder fell into the pond), so answer A makes sense. (When the boulder landed at the bottom of the pond and couldn't move any more, it's kinetic eneregy was transformed back into potential energy... but the question deals with what was happening at the top of the cliff!)
