system
Given the following post, respond as if you're commenting on Reddit:
human
Supernova explosions are caused by the star's matter collapsing in on itself and then bouncing back out. This matter moves beyond the initial radius of the star. Where does this energy come from that allows this star matter to travel out into the universe?

Just like how a ball won't bounce back beyond its original point of release, or how a pendulum will never swing past its original position. Where does this energy come from in the case of the matter that is flung away from dying stars?
gpt
Largely from the gravitational potential energy released by collapse. 

When the core implodes, it allows the outer layers to fall farther in, and when they hit during the 'bounce' phase energy is transferred from the core onto the infalling matter. Ultimately, that proto-neutron star that exists in the collapsed core is far more tightly gravitationally bound than the iron core which preceded it. About 1% of that energy is transferred to the outer layers, driving the supernova. The remaining 99% is radiated as neutrinos (so, fun fact, that means supernova are actually 100x more energetic than you would think just by looking at their light!)