21did u finish optics, sound, wave ??
Q1)A particle having charge 2=10^-4 C is placed directly below and at a separation of 10cm from a bob of simple pendulum at rest.The mass of the bob is 100g.What charge should the bob be given so that the string becomes loose.
Q2)Two identical charged particles are fastened to two ends of a spring of spring constant k=100N/m and natural length 10cm.the system rests on smooth tableif charge on each particle is 2*10^-8C.find extension in string.ASSUME EXTENSION IS SMALL AS COMPARED TO NATURAL LENGTH.I just want to know why did we assume the above condition and not the entire solution.
q3)Whenever a charged particle performs SHM,what is the force driving it.A single force can be either attractive or repulsive os is it for three particle system.
-
UP 0 DOWN 0 0 3
3 Answers
211) mgl^2/K q ( K = 1/4pi E) its just the force of repulsion = wt of bob
2)if we didnt assume that x<<l, the equation would bcome
q^2/{(l+x)^2 (4 pi E0)} = Kx
as solution is bcming tough ,we assumed that x<<<<l, and wrote it as
q^2/{l^2 (4 pi E0)} = Kx now we get the solution easily......