Fan (machine) the airflow from the fans. Thus, fans may become ineffective at cooling the body if the surrounding air is near body temperature and contains high humidity. The punkah fan was used in India about 500 BCE. It was a handheld fan made from bamboo strips or other plant fibre, that could be rotated or fanned to move air. During British rule, the word came to be used by Anglo-Indians to mean a large swinging flat fan, fixed to the ceiling, and pulled by a servant, called the punkawallah. For purposes of air conditioning, the Han Dynasty craftsman and engineer Ding
Ant on a rubber rope Consider a variation in which the rope stretches suddenly and instantaneously before each second, so that the target-point moves from formula_3 to formula_11 at time formula_5, and from formula_11 to formula_14 at time formula_15, etc. Many versions of the problem have the rope stretch at the "end" of each second, but by having the rope stretch before each second we have disadvantaged the ant in its goal, so we can be sure that if the ant can reach the target-point in this variation then it certainly can in the original problem or indeed in variants where the rope stretches at