Seesaw a "teeter-totter". According to linguist Peter Trudgill, the term originates from the Nordic language word "tittermatorter". A "teeter-totter" may also refer to a two-person swing on a swing seat, on which two children sit facing each other and the teeter-totter swings back and forth in a pendulum motion. Both "teeter-totter" (from "teeter", as in "to teeter on the edge") and "seesaw" (from the verb "saw") demonstrate the linguistic process called reduplication, where a word or syllable is doubled, often with a different vowel. Reduplication is typical of words that indicate repeated activity, such as riding up and down on a
Playground surfacing injuries, according to the American Academy of Orthopedic Surgeons. More than half of these injuries result from falls to a playground surface that can cause fractures, concussions, dislocations, and internal injuries. Recognizing these facts, many organizations, including the Consumer Product Safety Commission, have issued guidelines and standards for playground surfaces. ASTM International has issued what it calls the “ASTM Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment”, which is known by its numerical designation, F1292. This standard accounts for both the deceleration of the head during impact and the length of time the head takes