In these equations, e refers to elasticity or coefficient of restitution--the ratio of relative speeds after and before a collision--varying between 1, a perfectly elastic collision, and 0, a perfectly plastic collision.

Although these outcomes suggest that people's judgments qualitatively mimic the expected output of the physical model, there is one important quantitative disparity: namely, the mean ratings are not smaller than the theoretical ratings that would be obtained given a perfectly elastic collision (e = 1).

5%) ignored the variations in chain length and based their responses on the launcher's drop height alone--which might reflect the assumption of a perfectly elastic collision model, or previous experience with the device.

A null effect of chain's length in the subjective ratings--non integration result--would signal either that people expect perfectly elastic collisions or that they are relying on a simple heuristic considering only launcher's impact velocity.

This is a general well-known result in the classical mechanics of elastic collisions valid even in relativistic mechanics) which we will make use of later.

2] can disappear by means of an infinitely denumerable number of elastic collisions, in each one of which the energy is conserved.