Where does rebound collide?

In physics, rebound is the bounce back of a body after it strikes another, and how much speed it keeps is captured by the coefficient of restitution, the ratio of the separation speed to the approach speed. Newton reported the origin of this idea in his 1687 Philosophiæ naturalis principia mathematica, where colliding pendulums were observed to fly apart with a relative speed in fixed proportion to the relative speed at which they met. Cross's 1999 The bounce of a ball measured this ratio for real balls on hard surfaces and showed how it changes with speed and material. The referent is a mechanical bounce governed by a measured ratio, not an economy's extra fuel use, a symptom returning after a drug, or a thought that comes back after being pushed away.[1][2]

Unit

A single collision, scaled by the coefficient of restitution from 0 (no bounce) to 1 (perfectly elastic)

Recovery means

Stored elastic deformation returns part of the impact energy as the body springs back

Measured by

Found by comparing separation speed to approach speed, often from high-speed video or drop-and-bounce height tests

In economics, the rebound effect is the tendency for gains in energy efficiency to be partly offset because a cheaper energy service leads people to use more of it. William Stanley Jevons first described this in his 1865 book The coal question, arguing that more efficient steam engines raised, rather than lowered, total coal consumption. Khazzoom's 1980 Economic implications of mandated efficiency in standards for household appliances gave the modern formulation, framing the effect through the price elasticity of demand for the energy service. The referent is a market and behavioural response measured as a share of expected savings, not a physical bounce, a symptom after a drug, or a suppressed thought.[3][4]

Unit

One efficiency improvement, scaled as the share of expected energy savings taken back through greater use

Recovery means

Not applicable

Measured by

Estimated from the price elasticity of demand for the energy service, or by comparing projected savings against observed consumption

In medicine, the rebound effect is the return, often in a stronger form, of the very symptoms a drug was holding down once the drug is stopped or its level falls. Kales, Scharf, and Kales named a clear case in their 1978 Rebound insomnia: A new clinical syndrome, showing that patients coming off certain sleeping pills slept worse than they had before treatment. They described this overshoot as a distinct withdrawal pattern rather than a simple relapse. The referent is a physiological overshoot tied to a withdrawn medicine, not a bouncing object, an economy's extra fuel use, or the resurgence of a suppressed thought.[5]

Unit

One course of treatment, scaled by how far the withdrawn symptom overshoots its pre-treatment level

Recovery means

Not applicable

Measured by

Assessed by comparing symptom severity after stopping the drug against the pre-treatment baseline, often in controlled withdrawal studies

In psychology, the rebound effect is the resurgence of an unwanted thought after a person has been trying to push it out of mind, so that suppression can leave the thought more available than if it had been left alone. Wegner, Schneider, Carter, and White demonstrated it in their 1987 Paradoxical effects of thought suppression, where people told not to think of a white bear thought of it more once the restriction was lifted. Their account traces the effect to a monitoring process that keeps searching for the forbidden thought and thereby keeps it active. The referent is a mental overshoot after deliberate suppression, not a physical bounce, an economy's extra consumption, or a symptom returning after a drug.[6]

Unit

One episode of attempted suppression, scaled by how much the target thought recurs afterward

Recovery means

Not applicable

Measured by

Counted as the frequency of the target thought after suppression, using think-aloud reports or streams of consciousness with a marker for each occurrence