Physics 118A
PROBLEM SET #1
Assigned: Mon.
. 1/14/08
Young & Freedman Chapter 21
Due Thur. 1/24/08
no later than 5:00 PM
Solve all problems algebraically, and only insert numerical values as the last step if
a numerical answer is required. Show all your work, and explain your reasoning.
Full credit will only be awarded if the correct answer is accompanied by an
algebraic solution and sound physical reasoning.
While we encourage free discussion of the homework, each assignment is to be
completed individually. Copying will not be tolerated.
________________________
 BOX FINAL ANSWERS

1. A positive point charge +0.65
μ
C exerts an upward force of 0.25 N on a point charge
Q
directly above it. The distance between the two charges is 0.35 m.
a) What is the
Q
? (You must give its magnitude and sign.)
b) What are the magnitude and direction of the force exerted by
Q
on the first charge.
2. In the ground state of the Bohr model of the hydrogen atom, the electron is in a
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This note was uploaded on 04/01/2008 for the course PHYS 118 taught by Professor Hohenberg during the Spring '08 term at Washington University in St. Louis.
 Spring '08
 Hohenberg
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