Two small plastic balls hang from threads of negligible mass. Each ball has a ma

Question

Two small plastic balls hang from threads of negligible mass. Each ball has a mass of .2g and a charge of magnitude q. The balls are attracted to each other, and the threads attached to the balls make an angle of 20 degrees with the vertical, as shown in the figure.

Part A-find the magnitude of the electric force acting on each ball.

Part B-find the tension in each of the threads.

Part C-find the magnitude of the charge on the balls.

Note: the balls are separated by 2.05cm and they have opposite charges( sorry i couldnt upload the picture, I will howerver if you cannot figure this out without it).

Explanation / Answer

Electrostatic force Fe = the horizontal component of the tension on the thread.
A. Fe = mg*tan(theta) = 0.2*9.8*9.8*tan(20) = 6.9911
B. Tension = sqrt((mg)^2+Fe^2) = 20.4407
C. To find the charge you would use the electrostatic force formula:
Fe = kq^2/r^2 ==> q = sqrt(Fe*r^2/k) = sqrt(6.9911*0.0205*0.0205 / 9 * 10^9)

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