Answer:
When the polythene rod is rubbed with the woolen cloth, static electric charges move from the cloth and into the rod. The rod becomes negatively charged as negative charges move from the cloth and into the rod leaving the cloth positively charged as well.
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Answer:
Lift is the upward force on the wing acting perpendicular to the relative wind and perpendicular to the aircraft's lateral axis. Lift is required to counteract the aircraft's weight.
Explanation:
Period, T = 1/ f.
f = frequency = 200 Hz.
Period T = 1/200 = 0.005 seconds.