# Physics 203 at Portland State 2015

## General Q&A

1. Can I type solutions on word doc and upload it to media manager?
• It's much more preferable to type straight into the wiki, so that others can edit it.
• Don't make it perfect all at once, but just start or continue something, and others will take care of it.
2. I posted a comment on Wiki. Do I have to write my name underneath it?
• No need to sign your name, unless it’s a personal question. The wiki software automatically keeps track of who edited what. Every few weeks or so I check that record and give you points.
Prof. Nicholas Kuzma 2015/04/13 13:08

## Immediate priority

Task Rough first pass “Make it look nice” edit Error check and fix
Create a class calendar for us (see below) Brittany D
Post solution to Problem 1.0
Post solution to Problem 1.2A Elin O Prof. Kuzma
Solve Problem 1.2A when k is unknown

Steps:

1. open a new g-mail account with an appropriate name (such as PSU.physics203.2015)
2. go to the calendar (http://calendar.google.com)
4. add all the dated events from the syllabus.
5. email Prof. Nicholas Kuzma the name and password for the account

### Having trouble?

Post your questions or tips below:

1. Question: I cannot figure out how to edit the already created calendar to add new items.
2. Question:
3. Question:

## Medium priority

Task Rough first pass “Make it look nice” edit Error check and fix

### Questions?

Post what's on your mind below:

1. Question:

## Wish list

Task Rough first pass “Make it look nice” edit Error check and fix

1. Question:

# Other postings

## Putting out fire with sound

I just found this interesting and relevant to what we are discussing in class. George Mason University engineers use low-frequency sound waves to put out a fire.

## Homework questions

1. Question:A 0.550-kg block slides on a frictionless horizontal surface with a speed of 1.40 m/s . The block encounters an unstretched spring and compresses it 23.0 cm before coming to rest. What is the force constant? I tried using $\frac{1}{2}mv^2= \frac{1}{2}kx^2$, but I couldn't figure out what x was. Then, I tried $k=\frac{mg}{x}$ and that wasn't the right answer either. — Brittany D.
2. Question:How do you know which direction a wave is travelling based on harmonic wave function equation (e.g. homework 14.23
• Answer: In the harmonic wave function equation look at the sign of x and t (– , +). If they have the same sign then the wave is travelling in the negative x direction.
• If x and t have different signs, the the wave is moving in the positive x direction.

Molly McCarthy 2015/04/14 10:47