Question #e14fb

1 Answer
May 28, 2016


The possibilities are infinite.


In this moment the gravity is acting on your body trying to press you down on the ground, But the electric charges of your atoms create structures that resist to the gravity balancing it.

In a nucleus of an atom the protons are all positively charged and tend to repel each other. The nucleus does not explode because at the same time there is the strong nuclear interaction that keeps the protons and the neutrons together.

My favorite is the experience of Millikan: he charged a drop of oil with electric charge and suspended it between two plates electrically charged. So on the drop of oil there were two forces acting: the gravity puling down and the electric field pulling up. When the drop stay floating at mid-air you know that the forces are of identical strength. Exploiting this idea Millikan was able to give an estimation of how strong was the electric charge on the oil drop that was a first measurement of the charge of the electron (but a full explanation is too long, search on Wikiledia the Millikan experiment).

In general, to solve this question you have to think about the four fundamental forces: gravity, electromagnetism, weak and strong nuclear forces.
Try to imagine, then, the cases where two or more of them two act together.