Sprettedynamikk

Sprettedynamikk, or bounce dynamics, is the study of the motion and forces that occur when a body collides with a surface and rebounds. In physics and engineering, it describes how energy is transferred between the body and the surface during contact, how the contact time evolves, and how the properties of the body and surface influence the rebound. The term is used in Norwegian-language texts to discuss phenomena observed in sports equipment, biomechanics, robotics, and computer simulations, as well as in teaching basic mechanics of impacts.

Key parameters include the coefficient of restitution e, which ranges from 0 (perfectly inelastic) to 1 (perfectly elastic). It relates the speeds before and after impact by v_after = - e v_before in the normal direction. The rebound height h' is related to the drop height h by h' = e^2 h in the absence of air resistance. Impact force and contact time depend on the stiffness of the colliding bodies and damping; models range from simple linear spring-dashpot to Hertzian contact with nonlinear stiffness.

In simple models, a rigid ball colliding with a rigid floor is represented as a mass-spring-damper system during contact; after separation, motion is ballistic. More sophisticated approaches incorporate surface compliance, spin, friction, and nonlinearity of contact.

Applications include analyzing bouncing balls and jump performance, designing sports equipment (balls, rackets, footwear), improving legged robots and prosthetics, and producing realistic animation in computer graphics.

Limitations include the effects of surface roughness, air resistance, spin, and material fatigue, which can all influence real-world bounce behavior. Sprettedynamikk is an interdisciplinary field that intersects collision dynamics, contact mechanics, and biomechanics.