Homework Assignment 4
Fall 2017
Total of 50 points
1. (20 pts total) In class we did an example with the electric field of two positive charges in line with each other. This problem will go one step further and add in two dimensions. The picture and questions will help walk you through this more complex problem.
· There are three protons acting on an electron at the origin. Each proton has a charge of 1e and is positioned 1nm from the electron, as shown below.
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a. (3pts) Draw a FDB for the electron. Just consider the forces of the protons
b. (1 pt) What direction do you think the electron will travel in due to the electric fields of the protons?
c. (2 pts) Because this is a 2D problem, write the two expressions that you will need to solve, i.e. Ex and Ey components.
d. (7 pts) Solve your equations for the electric field acting in both directions.
e. (5 pts) What is the force acting on the electron due to the resulting electric field?
f. (2 pts) Does this answer agree with your prediction in part b? (if it does not agree, DO NOT change your answer for part b. I want to see your initial thoughts with this problem)
2. (40 pts total) You have two vectors and
a. (10 pts) What is ?
b. (10 pts) What is ?
c. (10 pts) What is ?
d. (10 pts) What is ?
+ -
+
+
r1 = 1 nm r2 = 1 nm
r3 = 1 nm
+
-
+
+
r
1
= 1nmr
2
= 1nm
r
3
= 1nm
dhvjn7l
hw4.docx
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