Strings (tennis)
The material used in tennis string can significantly affect a player's performance, and even health. Several materials are used to make tennis strings. They vary in terms of elasticity, durability, rebound efficiency, tension holding capability, and manufacturing cost, among other considerations.
String trimmer
A string trimmer works on the principle that a line that is turned fast enough is held out from its housing (the rotating reel) very stiffly by centrifugal force. The faster it turns the stiffer the line. Even round-section nylon line is able to cut grass and slight, woody plants quite well. Some monofilament lines designed for more powerful cutters have an extruded shape, like a star, that helps the line slash the material being cut; the line is thus able to cut quite large woody plants (small shrubs) or at least ring-bark them very effectively. These lines make disks less necessary for tough jobs.