Two colliding objects {collision}| have compressive force. Initial positions and velocities cannot be precise, but deviations are small, so future behavior mostly predictable. For collisions between three objects simultaneously, future behavior can deviate far from predicted behavior. If first two objects collide first, followed by third object, resulting motions can be much different than if last two objects collide first, followed by first object.
If two dense hard objects collide, all energy stays in motion, no heat is made, and objects bounce off each other {elastic collision}|. In elastic collisions, forces are equal and opposite, and momentum (m*v) before and after collision is constant: m1 * v1 = m2 * v2. In elastic collisions, with no heat, total energy E is kinetic energy KE plus potential energy PE and stays constant: E = KE1 + PE1 = 0.5 * m1 * v^2 + m1 * g * h1 = 0.5 * m2 * v^2 + m2 * g * h2 = KE2 + PE2.
examples
Superballs are denser and harder than regular balls. Karate experts try to make elastic collisions, rather than inelastic collisions, to break objects. Atomic-particle collisions are elastic, because they do not deform.
If either colliding object is soft or has low density, collision {inelastic collision}| permanently deforms surface, some collision energy becomes heat, and objects can stick together.
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Date Modified: 2022.0225