GEN PHYS 2 | Solutions & Solving Guide

Relevant Constants

e=1.6\times10^{-19} | elementary charge or the charge of one electron
k=9.00\times10^9\frac{N\cdot m^2}{C^2}=\frac{1}{4\pi\epsilon_0} | Coulumb’s constant
\epsilon_0=8.854\times10^{-12}\frac{C^2}{N\cdot m^2} | permitivity of free space
1C=8.25\times10^{18} electrons
1nC=1.0\times10^{-9}C | the charge of one nanocoulumb
- putting “n” before an SI unit entails expressing the value in scientific notation where 10 is raised to -9

1\mu C=1.0\times10^{-6}C | the charge of one microcoulumb
- putting “\mu ” before an SI unit entails expressing the value in scientific notation where 10 is raised to -6

F=k\frac{\left|q_1q_2\right|}{r^2}

The forces that two charges apply onto one another are always along the line joining them.
Use the direction the charges move as a way to check the direction of the forces between them.
If the charges are collinear or on the same line, add/subtract them algebraically.
If the charges are at a right angle or at two different directions, use the pythagorean theorem and trigonometry.
If the charges acting on a certain charge are equal in magnitude and distance, the forces may cancel out due to symmetry.

n=\frac{Q}{e}