Two small metallic spheres, each of mass 0.28g are suspended as pendulums by light strings from a common point as shown. The spheres are given the same electric charge, and it is found that the two come to equilibrium when each string is at an angle of 5.1 degrees with the vertical. The Coulomb constant is 8.98755e9 and the acceleration of gravity is 9.81. If each string is 22.5cm long, find the magnitude of the charge on each sphere. Answer in units of nC.(adsbygoogle = window.adsbygoogle || []).push({});

sin 5.1 = x/.225 x=.02m

mg = (kq^2)/r^2

(2.8e-4)(9.81) = ((8.98755e9)q^2)/(.04^2)

q=2.2113e-8 C = 22.113 nC

My answer is wrong and I don't understand why.

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# Homework Help: Pendulum w/electrostatic force

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