SC12-01: Trebuchets!

On Thursday, April 9, the day before break, we watched the Nova special Medieval Siege. A large number of students were absent, so I am announcing this on the blog - the subject matter of the video will make an appearance on our next quiz. If you were absent, you may get some details about the special at the link above. No one will be exempted from the quiz.

Homework: 04/01/09 - 04/08/09

SC12: Physics
Day 1/2: Sound Intensity & Resonance
HW: Doppler Problems; P. 488: 13A; 1, 3, 5
Day 3/4: Standing Waves on a String; Beats
HW: P. 499: 13B; 3; P. 503: 3
Day 5/6: Exam: Waves & Sound
HW: Read Pp. 496 - 499: Standing Waves in an Air Column

SC12P: AP Physics C (Mechanics)
Day 1: Conservation of Angular momentum
HW: Pp. 331 - 332: 21, 25, 29, 37
Day 3: Static Equilibrium
HW: P. 353 - 358: 1, 2, 11, 19
Day 5: Review
HW: Study for the Exam
Day 6 Lab: Exam: Rotation & Angular Momentum

Auditory Illusions

Your ears can be fooled. Pitch, which is related to the frequency of sound, is a subjective sensation in which you - the listener - assign perceived tones to relative positions on a musical scale. The relative perception of pitch can be fooled, resulting in auditory illusions, which are the aural equivalent of optical illusions.

First up, here are some optical illusions that are equivalent to the auditory illusions you are about to hear:

• The Necker Cube
• The Dancer's Silhouette

These two illusions occur because we are presented with ambiguous two-dimensional information, but our brains assume the shapes are three-dimensional and assigns a direction to the apparent rotation. This direction is artificial and can, with practice, be made to change direction at will.

Now, for the auditory illusions:

• The Tritone Paradox
• The Shephard Scale

The tritone paradox is the auditory equivalent of the above optical illusions. The perceived changes in pitch are artificial, and depend in part on where the listener grew up. Also, people with a musical background tend to hear them differently than non-musical listeners. Again, with practice the perceived changes in pitch can be made to reverse. In the Shephard scale, a continuous sequence of specially formed tones can be made to sound as if it continues ascending or descending forever.

Finally, one of my favorite auditory illusions is the speech-to-song illusion, where a section of a spoken sentence, when repeated often enough, suddenly appears to be sung.

Have fun!

AP Physics - Vector Cross Products

Here are a couple of useful tools for working with vector products. The first is an applet from Syracuse University that helps you visualize the cross product of two vectors in three dimensions, and the second is a handy little vector calculator that calculates cross products, dot products, and allows you to visualize the vectors.

• Vector Cross Product in 3-D
• Vector Calculator

Both applications have been added to the applet list on the right side of this page.

One other link of interest is this one from Yahoo! Answers that tells those of you too lazy to look it up how to calculate cross products on your TI-89:

• Cross Products on the TI-89

Homework: 03/24/09 - 03/31/09

SC12: Physics
Day 1/2: Interference, Reflection, Standing Waves
HW: P. 465: Section Review; 1 - 5
Day 3/4: Sound Waves, Doppler Effect, Wave Quiz
HW: P. 486: Section Review; 1 - 4
Day 5/6: Sound Intensity & Resonance
HW: P. 488: 13A; 1, 3, 5

SC12P: AP Physics C (Mechanics)
Day 1: Vector (Cross) Product
HW: P. 330: 1, 3
Day 3: Angular Momentum
HW: Pp. 330 - 331: 11, 13, 14, 17, 19
Day 5: Conservation of Angular momentum
HW: Pp. 331 - 332: 21, 25, 29, 37

Physics Course Survey

Please click the appropriate link below and complete the Survey Monkey course review.

• A-Block Physics Survey (survey ended; link disabled)
  
• G-Block AP Physics Survey (this link will be disabled at 9:30 am 04/01/09)

Thanks,
~G

Homework: 03/16/09 - 03/23/09

SC12: Physics
Day 1/2: Hooke's Law; Simple Harmonic Motion
HW: P. 441; 12A: 1 - 4
Day 3/4: Properties of a Pendulum
HW: P.449; 12B: 1, 3
Day 5/6: Properties of Waves
HW: P.457; 12D: 1, 4

SC12P: AP Physics C (Mechanics)
Day 1: Rotational Kinematics
HW: Pp. 299- 300: 1, 5, 11, 17
Day 3: Rotational Kinetic Energy; Moments of Inertia
HW: Pp. 301 - 302: 21, 23, 26, 31
Day 5: Torque & Rotational Work
HW: Pp. 302 - 303: 33, 37, 43, 44

We're Back! Homework: 02/02/09 - 02/09/09

Have you ever noticed that if you put something off for a day, it's easy to put it off for a week, and if you put it off for a week, it's easy to put it off for a month? Or even a few months?

Sorry about that.

Anyway, here are the assignments for the current cycle:

SC12: Physics
Day 1/2: Electric Potential Energy, Voltage
HW: Read Ch. 18
Day 3/4: Capacitance & Capacitors
HW: P. 681, 18C: 1, 3
Day 5/6: Electric Current & Resistance
HW: Current worksheet

SC12P: AP Physics C (Mechanics)
Day 1: Isolated and Non-isolated systems
HW: Pp. 218 - 219: 3, 4, 7
Day 3: Situations Involving Kinetic Friction, Conservation of Mechanical Energy
HW: P. 220: 13, 19; P. 224, 54
Day 5: No Class - Senior Thesis Project committees
HW: n/a
Day 6: Power
HW: P. 221: 30, 32; P. 224: 59, 62