GUJCET 2014 Physics Solved Paper

Two spheres having same radius and mass are suspended by two strings of equal length from the same point, in such a way that their surfaces touch each other. On depositing charge 4×10−6C on them they repel cach other in such a way that in equillibrium the angle between their strings becomes 60∘. If the distance from the point of suspension to the center of the sphere is 10‌cm. Find the mass of each sphere. (K=9×109‌SI. and g=10ms−2.)