Intro to Springs

Today we derived Hooke's Law with a little intro lab:

Spring Intro Lab

We also revisited the equation for the potential energy stored in a spring.

The lab is technically due next time I see you, but a lot of people were able to finish in class and turn it in. You do have homework:

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

Also bring your lab notebook Monday/Tuesday.

Rotational Dynamics Test

Test day! No homework, but we are doing a lab tomorrow.

Senior Debates

The Senior Debates were today, so I did not even see periods 1, 2, or 3. Periods 5 and 6 had work time.

Practice Test

Your test for this unit will be on Thursday. Wednesday will probably be totally eaten up by the Senior Debates, so today is your day to study for your test.

Rotational Dynamics Test Practice

Abridged answers

I also have some videos, but they are for an older version and some of the problems have changed.

#4
#5
#7 (PART C HAS CHANGED)
#8
#9 (energy method), #9 (dynamics method) (THIS HAS CHANGED)
#10
#11 (THIS HAS CHANGED)

More Angular Momentum

Today we started with a conservation of momentum problem, then learned a "magic" trick involving a ring and a necklace, played with a gyroscope, and finally we watched a couple of videos that use angular momentum to explain real-world stuff:

Why cats land on their feet - Smarter Every Day
Aerial Skiing - The New York Times

Homework: Ch.8 (p. 271) #58, 61, 72

I also had your practice test ready today, so you may have picked one up.

Angular Momentum

We had very little notes today, so I decided not to make a Powerpoint. Instead, I'll take pictures of the board as we go and post them here as soon as possible. For now I have some pictures from last year below.

Homework is Rotational Motion TIPERs #8
+ Ch. 8 (p. 271) #55 (look up the mass, radius, and orbital radius of Earth with The Google) & 62

Finding the angular momentum of a bike wheel:

Finding the angular momentum with a clump of mud sticking to the rim of the wheel:

Finding the new angular speed of a star that has shrunk dramatically:

One last picture with all of the equations:

Rotational Kinetic Energy

Today we learned about rotational kinetic energy and did some problems with it:

Notes: Rotational Kinetic Energy

Homework is Rotational Motion TIPERs #7 and Ch.8 (p. 270) #47 & 50

Practice and Mobile Turn-In

Your mobile projects are due today! Because needed class time to check mobiles, you spent the period practicing some problems that cover everything we've done so far this unit. We have two more topics to cover starting tomorrow, so this serves as a way to cement what we've learned so far.

The test this unit is currently scheduled for next Thursday, January 28th (the day after senior debates).

If you didn't finish the practice problems in class, they are homework:

Chapter 8 (p.263) CONCEPTUAL #6 & 12, + PROBLEMS (p. 268) #30, 70, 74, 78

Combining Linear and Rotational Dynamics

Today we were supposed to have a lecture about this, but I knew I'd be absent today so I made a video lecture instead and watching it was your homework last night. Here it is again (in two parts):

Part 1: YouTube, Dropbox (to download)
Part 2: YouTube, Dropbox (to download)

In class, you are doing all the problems that you were meant to do for yesterday's lecture and today's lecture:

Ch. 8 (p.269 ) #33, 35, 39, 40, 87

More on Moment of Inertia

Yesterday we defined and practiced finding the moment of inertia for point masses. Today we talked about the moment of inertia of extended objects such at rods, spheres, and disks.

Notes: More on Moment of Inertia

I will be gone tomorrow, so tonight's homework is to watch the lecture we would have done tomorrow:

Part 1: YouTube, Dropbox (to download)
Part 2: YouTube, Dropbox (to download)

Newton's Second Law for Rotation

Remember Newton's Second Law? Turns out there's an equivalent for rotational motion!

Notes: Torque and Angular Acceleration

Remember that your mobile is due Tuesday, but you can bring it in anytime before that as well.

Tonight's homework:

Rotational Motion TIPERs #5 (started in class)
Ch, 8 (p. 269) #31 & 32

Mobile Work Day

Today is your only in-class time to work on the Mobile Project. This is due Next Tuesday after the Martin Luther King, Jr. day weekend.

Here are some instructions that ended up on the board:







If you use standard units for everything, you should get a net torque of less than 0.001 N-m for each level. If you get something larger than that, you need to justify it by explaining errors that occured and how they would have affected your net torque calculations.

You do not have any additional homework tonight.

Torque and Equilibrium

Today we talked about the conditions necessary for equilibrium. That is:

Net force = 0
Net torque = 0

We did a problem together and Rotational TIPERs #4.

Homework is Ch.8 (p. 265) #8 & 21

We also passed out the instructions for our Mobile Project, which will be due on January 19th. You will have the next class period to work on this, but no other class time.

Torque

We spent the first part of class going over your labs from yesterday, then used your ideas from that lab to come up with the equation for torque. The notes ended up on the board, not in a Powerpoint:




We then worked on Rotational Motion TIPERs #2 and Rotational Motion TIPERs #3 (email miss.volkening@gmail.com for copies).

Homework is Chapter 8 (p. 264) #2 & 3

Note: if you were absent and unable to present today, I need to check your lab in your lab notebook.

Torque Lab

Today we completed a short lab:

Torque Lab

Your homework is to finish up your graph and explanation about the slope and y-intercept. Tomorrow your group will briefly present your results.

Center of Mass

Welcome back! Today we talked about the center of mass: what it is, how to find it, and some cool things we can do with it.

Notes: Center of Mass

We also completed this short qualitative lab:

Choose at least 3 different cardboard pieces. Sketch them in your lab notebook and qualitatively find their centers of mass. Write a brief description of your procedure and mark the COM on your sketches in your notebook.

Your book does not have many problems involving only the center of mass, so I had to make up a problem. Your homework is:

1.A uniform meter stick has a mass of 0.20kg.

a)Where is its center of mass?

b)A 0.30 kg mass is taped to the meter stick at the 80 cm mark. Now where is the COM of the system?

+Ch.8 (p. 272) # 69

Also, a few of you asked for the address of the planets simulation some classes looked at:
My Solar System