Ratio of separation to approach speed; describes how elastic an impact is.
e=(v₂'-v₁')/(v₁-v₂) is the ratio of relative separation speed to approach speed. e=1 is perfectly elastic and e=0 perfectly plastic. With momentum conservation it solves collision speeds.
A ball dropped from 1 m with e=0.8 rebounds to 0.64 m.
The coefficient of restitution summarises how much energy an impact keeps, which is needed for realistic impact and bounce models.
Ratio of separation to approach speed; describes how elastic an impact is.
The coefficient of restitution summarises how much energy an impact keeps, which is needed for realistic impact and bounce models.
Drop the object onto a hard surface and divide the rebound speed by the impact speed, or use a high-speed video to measure approach and separation.
No. A value of one means a perfectly elastic collision, and values below one mean energy is lost.
Typical applications include choosing a material for a bouncing ball or a protective surface, predicting the bounce height of a dropped steel ball on a plate and modelling the impact of a bolt falling onto a metal floor.
Study "Collisions" first (topic 32 of 106 in Engineering Mechanics). It covers the groundwork this topic builds on.
Between 0 and 1. Depends on materials. Energy loss ∝ (1-e²).
A ball dropped from 1 m with e=0.8 rebounds to 0.64 m.
The next topic is "Kinematics of rigid bodies", which builds directly on this one.
It is classed as Beginner in Engineering Mechanics (topic 33 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.