balls

Balls are round or spherical objects used in games, recreation, and science demonstrations. In geometry, a ball refers to the set of points at or within a given distance from a center; the surface is a sphere. Most balls are nearly perfect spheres with a uniform mass distribution. They may be solid or hollow, and many are inflatable with an internal bladder to hold air or other gas.

They come in many forms, including sports balls (soccer, basketball, football, baseball, tennis, golf, cricket, volleyball, rugby), toy balls (plastic beach balls, rubber bounce balls), and fitness or medicine balls. Materials used range from natural and synthetic rubbers to leather and various polymers. Construction methods vary, with some balls having stitched panels, others molded shells, and some fabric coverings. Physical properties such as elasticity, mass, and surface texture influence bounce, grip, and control; the coefficient of restitution governs how much energy is preserved in impact.

History and manufacturing: Balls have ancient origins in various regions, with evidence of early leather- and rubber-covered spheres. Modern production employs precision molding, paneling, or composite construction, and many sports specify standard sizes and weights. Practical design aims to balance durability, bounce, handling, and durability under repeated impacts and environmental conditions.

In everyday use, the concept of a ball is central to many games worldwide and serves as a basic example in demonstrations of motion, force, and energy transfer.