As I understand the law of inertia, an object in motion tends to stay in motion, particularly in outerspace. And when one considers the extraordinary force and speed with which a Supernovae explodes, surely all of that plasma and matter should be flying away at incredible speeds for infinity. So, how then, in nebula where Supernovae occur, does any of the matter that exploded out remain in it? Shouldn't it just force its way out at incredible speeds, forever? As the materials that are jettisoned are essential in creating solar systems, because of their heavier elements, I'm just uncertain how these powerfully accelerated particles could be made to conveniently stick around, when they need to. Does anyone know how that works?
The only supernovae that totally destroy themselves, without a massive core collapsing to form a neutron star, magnetar or black hole, are pair-instability (hypernova) and type 1a supernovae (based on various scenarios involving accretion of matter onto a white dwarf or collision of white dwarfs, where the core does not collapse). You also misunderstand Newton's first law of motion, which states what happens in the absence of external forces. A particle of supernova ejecta is subject to the gravitational attraction of the core remnant and the remainder of the supernova ejecta, but as the initial ejection velocity is typically 10% of the speed of light (30,000 km/s), gravitational deceleration is not significant. However, subsequent deceleration is largely due to interaction with the interstellar medium, forming shock waves, which can trigger new star formation. http://www.physicsclassroom.com/class/newtlaws/Lesson-1/Newton-s-First-Law Multiple supernova explosions in the same region and pair-instability supernovae can carve out superbubbles across the depth of an entire galactic arm. https://en.m.wikipedia.org/wiki/Superbubble