SHM Practice Problems

Today you worked on practice problems while I was in meetings elsewhere.

Ch. 13 Conceptual (p.465) #1, 2 + Problems (p. 467) #19, 21, 24, 25, 28

Anything you don't finish is homework, and we will go over your period of a pendulum labs tomorrow. Please have them done.

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 20 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.

Mechanical Waves

Because I will be out next Wednesday, I have had to rearrange some things, and that means today we are taking a little break from SHM to talk about mechanical waves. We will go back to SHM on Monday/Tuesday with another lab, so bring your lab notebook next time. I will also be checking your Period of a Spring Lab on Monday/Tuesday.

Here are the notes for today:



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

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

Here is the stuff about earthquakes:
Types of Seismic Waves (L. Braile, Purdue)
Seismic Waves (YouTube)


Homework: Ch. 13 (p.469) # #41, 42, 44.

Circles and SHM

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

Springs and Simple Harmonic Motion

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: HW: Period of a Mass/Spring System

Lab: Period of 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 (tip: if you set the friction to "lots" for this part, it will keep the mass from bouncing and let you measure the stretch more easily). 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.

Springs

Today we used your labs to figure out Hooke's Law...which we actually learned and took notes on back in October. We also talked about ways the model of springs can be used to explain concepts that don't necessarily look like springs.

Dolphin Tails
Chemical Bonds
Robert Hooke

Homework: Chapter 13 (p.466) #1, 4, 5

Also bring your lab notebook Monday/Tuesday.