Obtain 3 identical small metal spheres, each suspended by silk thread. Measure the mass of the spheres. Pass the thread from 2 of the spheres through a small loop and tie off the thread equally above the loop. Develop a system so you can raise and lower the loop along the thread between the tie point and the spheres. Obtain a metal rod with an insulating handle and then give this rod an electric charge by rubbing with fur. Pull the thread of one sphere off to the side and touch that sphere with the rod. Then allow the 2 spheres to touch. The 2 spheres then will equally share the charge that the one had and repel each other. By measuring the geometry of the spheres (the separation and the angle between the 2 threads) you will be able to calculate the repulsive force. Now adjust the position of the loop so that the distance between the spheres changes. Repeat the geometry analysis. You should find that the force change confirms the inverse square part of the law.

Now take the 3rd sphere (with neutral charge) and allow it to touch one sphere of the charged pair. Repeat the force analysis. You should find that the repulsion force decreased by 1/2. This confirms that the force is proportional to product of the charges.

Does anyone know how the geometric analysis would work specifically?:D

The two threads holding up the spheres would separate by an angle . If you do a force balance calculation on the sphere of mass you find that the repulsive force is:


If the repulsive force is proportional to the inverse square of the distance between the spheres, then you should find that:



where k is a constant.

What is g?

Quote:

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Originally Posted by spacefire5458

what is g?

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Acceleration due to greavity - approximately 9.8m/s^2 for those of us who live at the surface of the earth.