bounce

Bounce is the movement of an object reversing its direction after colliding with a surface and moving away from it. In physics, the rebound is quantified by the coefficient of restitution, e, defined as the ratio of speeds after and before impact along the line normal to the contact surface. Values range from 0 (perfectly inelastic, no rebound) to 1 (perfectly elastic, no energy loss).

The rebound depends on material elasticity, surface hardness, contact time, and deformation of the bodies involved. When a ball strikes a surface, part of the kinetic energy is stored as elastic potential energy and then returned; energy is also dissipated as heat, sound, and internal friction, reducing e below 1.

Applications include sports and design. Objects are engineered for desired bounce characteristics, such as high-bounce basketballs, tennis balls, and trampolines, where surface structure and materials influence e. In engineering, bounce behavior informs impact testing, cushioning, and vibration isolation.

Other uses of the term exist outside physics. In web analytics, bounce rate indicates the proportion of visitors who leave a site after viewing only one page. In communications, an email bounce occurs when a message cannot be delivered. In finance, a bounced check is one that cannot be honored due to insufficient funds.