Mechanical Waves

Class today was only 33 minutes long, so we did a short introduction to mechanical waves:

Here is a website with animations of the different kids of mechanical waves:

Acoustics and Vibrations Animations, Daniel A. Russell, Pennsylvania State University

No homework tonight.

I will be gone tomorrow, so the sub plan is for you to read and take notes on p. 458-460 then work on homework problems. You may want to do the reading and taking notes tonight so you don't have to bring your book tomorrow.

Period of a Pendulum

Today we used your lab results to get the equation for the period of a simple pendulum. We also watched a fun pendulum video and mentioned physical pendulums.

Notes: Pendulums

In case you can't access the Powerpoint, here are the links for the videos we watched:


Harvard Natural Sciences Lecture Demonstrations: Pendulum Waves
Memo Akten: SHM #2 Excerpt
Somewhere in here we also talked about speed walking and pendulums, so here is a video of speed walkers.

Homework is Ch. 13 (p. 468) #34, 35, 39

Lab: Period of a Pendulum

Today we basically did the same lab as last week, except for a pendulum instead of a spring on a mass:

For any linear graphs you get, try to figure out what the slope represents. Also, don't displace the pendulum by more than 25 degrees.

If you were gone, there is a very nice pendulum simulation here: PhET Pendulum Lab. There is even a lovely photo gate timer that you can turn on that will measure one period for you. If you prefer a standard stopwatch, one will appear if you turn on "other tools."

No extra homework tonight; just get the lab totally finished.

SHM Practice Problems

Today we worked on practice problems all day. These are due next class:

Ch. 13 Conceptual #1, 2 + Problems #17, 19, 21, 24, 25, 28

Some people finished their labs so I could check them or took the retake exam. I had to submit progress report grades after school.

Bring your lab notebook next class!

SHM and Circular Motion

Today we used circles to model simple harmonic motion, which gave us some equations for the position, velocity, and acceleration of an object undergoing SHM. We also talked about angular frequency.

Notes ended up on the board (below) and we used these sites to look at the motion:

UNSW School of Physics PhysClips: SHM Background Material

Teresa Martin Physics Flash Animations

If we had time we also watched this (just because it's cool).

Homework is Chapter 13 (p. 467) #12, 18, 22

SHM: Period and Frequency

Today we used the results from your lab to get an equation for the period of a mass on a spring. We also took a little bit of notes beyond that:

Notes: Simple Harmonic Motion

Homework is a little half-sheet worksheet I made: 2/4 HW. There is a ranking task on the back side that I cannot reproduce online, so you'll have to get a hard copy in class.

Lab: Period of a Mass on a Spring

Today you completed a lab to determine what and how quantities affect the period of oscillation for a mass on a spring.

Lab: Finding T for a Mass on a Spring

No extra homework tonight, but this lab is due Wednesday.

We ended up with some hints on the board, so there is a picture of it below.

If you missed the lab or didn't get enough data at home, there is an online simulation here:

PhET Mass-Spring Lab

To use it you need to make sure the "friction" is set to zero, time is set to "real time" and the planet is "earth." Use the spring on the far right and change its k value by moving the "softness spring 3" slider. You will have to find the k for each "softness" level by hanging a known weight on the spring and measuring how far it stretches. Then k = mg/x. Finally, you'll need more masses that the labelled ones provided, so I found the masses of the unlabeled colored masses for you: green = 70g, gold = 160g, red = 300g.