University:
Boston University
Course:
CAS PY 105 | Physics 1
Academic year:

2022
Views:

449

Pages:

1
Author:

Yuliana Rice

Physics Challenge Solutions: Part 1 We can find the gravitational attraction using the universal law of gravity. The electrostatic attraction between the two is given by Coulomb’s law. Both are really small forces by everyday standards, but notice how much bigger the electrostatic force is: So, the electric force is 1039 times stronger; gravity seems negligible in comparison! Part 2 All matter is made up of protons, electrons, and neutrons. Even though the neutrons are neutral, the protons and electrons can interact through the electrostatic force, which, as we just saw is stronger than gravity. Yet, somehow, gravity determines how most matter moves around the universe. The reason is that, over length scales much larger than the atom’s size (about 10-10 m), the charges in each atom cancel each other out! (All atoms have the same number of protons and electrons, so from far away, they “look” neutral.) Therefore, the small contribution from gravity is all that remains.