Collision Theory – Coefficient of Restitution for Inelastic Impacts For inelastic bodies undergoing impact, what is the typical range of the coefficient of restitution e?

Difficulty: Easy

Correct Answer: between zero and one

Explanation:


Introduction / Context:
The coefficient of restitution e quantifies how “bouncy” a collision is by comparing relative speeds after and before impact. Understanding its range distinguishes elastic, inelastic, and perfectly inelastic collisions in dynamics problems.



Given Data / Assumptions:

  • Two bodies collide along the line of impact.
  • No external impulse acts during the very short impact interval.
  • e is defined along the common normal at impact.



Concept / Approach:
By definition, e = (relative speed of separation) / (relative speed of approach). Its value categorizes collisions: e = 1 (perfectly elastic), 0 < e < 1 (inelastic), e = 0 (perfectly inelastic, bodies stick together). Values e > 1 indicate impact with added energy (e.g., active systems) and are not typical for passive mechanical impacts.



Step-by-Step Solution:
Identify inelastic collision: some kinetic energy lost. Use definition: inelastic ⇒ 0 < e < 1. Perfectly inelastic special case: e = 0. Hence for inelastic bodies in general, e lies between 0 and 1.



Verification / Alternative check:
Examine energy loss: elastic collisions conserve kinetic energy; inelastic collisions do not. Since speed of separation is reduced relative to approach, the ratio e must be less than 1 but nonnegative.



Why Other Options Are Wrong:
zero only: corresponds to perfectly inelastic, not all inelastic. one only: elastic, not inelastic. more than one / less than zero: not applicable to passive mechanical collisions modeled without active energy input.



Common Pitfalls:
Confusing “inelastic” with “perfectly inelastic”. Misapplying e across tangential directions instead of the line of impact.



Final Answer:
between zero and one

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