why do ping pong paddles have two different sides
Table tennis racket Table tennis regulations approved by the International Table Tennis Federation (ITTF) allow different surfaces on each side of the paddle for various amounts of spin (including nullifying it) or speed.[1] For example, a player may have a spin-heavy rubber on one side of his paddle, and no spin on the other side. The player can flip the racket in play for different types of returns. To help a player distinguish between different types of rubber used by his opponent, regulations specify that one side of a paddle must be red while the other must be black, allowing a player to see what side of a paddle hits the ball mid-play. The player has the right to inspect his opponent's racquet before a match to see the type and color. Current rules state that, unless damaged in play, the paddle cannot be exchanged for another at any time during a match.[2]
Golf ball In 1848, the Rev. Dr. Robert Adams Paterson (sometimes spelled Patterson) invented the gutta-percha ball (or guttie, gutty).[4][5] The guttie was made from dried sap of the Malaysian sapodilla tree. The sap had a rubber-like feel and could be made round by heating and shaping it in a round mold. Because gutties were cheaper to produce, could be re-formed if they became out-of-round or damaged, and had improved aerodynamic qualities, they soon became the preferred ball for use.[6][7] Accidentally, it was discovered that nicks in the guttie from normal use actually provided a ball with a more consistent ball flight than a guttie with a perfectly smooth surface. Thus, makers began intentionally making indentations into the surface of new balls using either a knife or hammer and chisel, giving the guttie a textured surface. Many patterns were tried and used. These new gutties, with protruding nubs left by carving patterned paths across the ball's surface, became known as "brambles" due to their resemblance to bramble fruit.