Plickers Day!

Today we did Plickers problems all day, in three sets. The first and second set were based on the topics this week. If you missed them, just turn in those associated howeworks (check Synergy).

The third set was 5 problems from secured AP practice exams, and covered stuff from the whole year. If you missed this, you can't really make it up, so they were extra credit.

Doppler Effect

The Doppler Effect is one of my favorite things!

Notes: Doppler Effect

Suggested homework is Ch. 14 (p. 505) Multiple Choice #12 + Conceptual #1, 7, 8.

We will have several Pickers problems tomorrow, covering stuff from this week and maybe some really old review too.

Test: SHM and Waves

Today was your test covering simple harmonic motion and waves. If you missed this test, please make it up by Tuesday so I can give them back.

Sound, Resonance, and Beats

Today was a conceptual day, with demos and videos involving waves and sound.

Notes: Sound Intro, Resonance, and Beats

Suggested homework is p.505 Multiple Choice #9 + Conceptual #6 & 11

For those that asked, here is the video of the boy breaking the glass:

Boy Breaks Glass With Voice

If you try this yourself, PLEASE wear eye protection and do not use someone's nice glasses. Go get some wine glasses from a thrift store or something.

Work Day

Today is your designated pre-test work day, though your test is next Wednesday, not Monday/Tuesday.

Here are the usual practice test, its key, and some old solutions videos (that I need to update).

SHM and Waves Test Practice

Solutions videos (note that the numbers of the problems have changed):
#9
#10 (part b is different)
#11
#12

Wave Interference and Reflection

Today we talked about what happens when waves overlap or hit a barrier/change mediums.

Notes
Simulations:
Zona Land Education: Wave Interference I
Zona Land Education: Wave Interference II
Zona Land Education: Wave Interference III
PhET: Wave on a String
Physics Classroom: Wave Interference Simulation

Homework: There is almost nothing to practice interference in the textbook, so your homework tonight is to play a game. Download the app Kerflux and get to at least level 30. Please note you do NOT have to pay anything for this game. If you do not have a device that can run Kerflux, that's okay too; I'm not actually checking this.

On Wednesday you will have a work day to prepare for your unit test.

Your unit test is next Wednesday, 2/26.

SHM and Waves Test Practice

Solutions videos (note that the numbers of the problems have changed):
#9
#10 (part b is different)
#11
#12

EM Waves

Today was a half day, so we very briefly discussed a type of non-mechanical wave called an electromagnetic (EM) wave.

Electromagnetic Spectrum
United States Frequency Allocations (NASA)

Homework: p. 468 #28 & 43

Mechanical Waves

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)


Suggested homework: p.469 #41 & 44.

Pendulums and SHM

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

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.

Here is a great video that explains how patterns are made using a pendulum with different periods in different dimensions of motion: YouTube: Sand pendulums - Lissajous patterns - part one // Homemade Science with Bruce Yeany. The explanation of how they work starts at 4 minutes in.

Practice problems: 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 15 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.

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).

Suggested homework is Chapter 13 (p. 467) #12, 18, 22. This was actually the wrong set, but by the time I realized that it was too late to change, so we're going with it. But next year...#18, 22, 28

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

Suggested homework is a little half-sheet worksheet I made: HW: Period of a Mass/Spring System

Work Day

I was out sick today, so you had time to finish up your graphs from your lab. I expect everyone to be done tomorrow.

Period of a Spring Lab

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.