Q. A smooth cylinder of radius=10 cm resting on a horizontal surface supports a bar AB of length 30 cm that is hinged at A. The weight of the bar is 50 N. The cylinder is kept from rolling away by a string AO of length 20 cm. Assume all surfaces to be frictionless, find tension in the string.
Q. In a certain vacuum tube, electron evaporate from a hot cathode at a slow steady rate and accelerate from rest through a potential difference of 45 V after that they travel 28cm. as they pass through an array of slits and fall on the screen to produce an interference pattern .If the beam current is below a certain value, only one electron at a time would be in flight in tube. What is this value? In this state, the interference pattern still appears showing that each individual electron can interfere with itself.