Help me please.......

Thread Starter


Joined Nov 19, 2007
Two small light balls, each of mass 2.0g and carring equal amount of like charge are suspended freely by light non-conducting string the length of each string is 13cm.The balls are in static equilibrium and separated by distance of 10 cm

Determine the charge carried by each ball..

Please give the solution of this question. Thank


Joined Apr 2, 2007
are the point from which the charges suspended same?
if so.
find the angle the strings makes(to horizontal or vertical) using the triangle formed by two 13 cm and one 10cm side.
now draw free body diagram of charge.
force of gravity acts downwards, force due to charge repulsion acts in horizontal direction and force due to tension in direction of string pointing towards the point of suspension.
since now the angle at which tension acts is know.
equate the vectorial summation of forces in horizontal direction to zero,
do the same for forces in vertical direction (if need be) to get the force due to repulsion.
u can also use Lami's formula.
now since force due to repulsion is known u can find out the charge using eqn for force due to charge.
m1 = m2 = 2.0g = 0.002kg q1=q2=q=? r=10cm=0.1m Fg=Fe so mg = qE or qkq/r.r =mg or q.q = mg.r.r/k or q2 = 0.002*9.8*0.1*0.1/9*10 raise to 9 now you use ur calculator solve ur answer. from this formula u find charge q by taking square root