Strength of the electric force imagine two 1.0-g bags of protons, one at the earth's north pole and the other at the south pole. (a how many protons are in each bag? (b calculate the gravitational attraction and the electrical repulsion that each bag exerts on the other. (c are the forces in part (b large enough for you to feel if yon were holding one of the bags?

(a) The mass of one proton is . Each bag has a mass of M=1.0 g=0.001 kg, so the number of protons in each bag is


(b) The distance between the two bags is twice the Earth's radius:


The gravitational attraction between the two bags is given by


To calculate the electrostatic repulsion, we should first calculate the total charge of each bag, which is the charge of one proton times the number of protons:


And now we can calculate the electrostatic repulsion between the two bags:


(c) we can easily see from point (b) that the gravitational attraction between the two bags is very tiny, so it cannot be felt. Instead, the electrostatic repulsion between the two bags is a very large number, so this can be felt.