Review for Test

The first thing we did today was to go over the paragraph-style answer on Rotation Motion TIPERs #7.

Your test for this unit will be a take-home test, which I will pass out on Thursday and will be due next Monday. 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 on 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 & 72 (note: there was originally another problem in this set, but I didn't like the confusing wording so you no longer need to do it)

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

Mobile Project Work Time

Today is your one in-class work day for your mobile project. Remember that you either have to show me your mobile in person or take a video of it spinning and show me the video. You need to turn in the blueprint and math showing that net torque is zero (or nearly so) for all levels. It is due on Wednesday.

Linear/Rotational Practice

Today we did one problem together. Below are the problems that various periods picked.

#39


#40 (this sets up a system of three equations and three unknowns, which you then need to solve)


#87 (this sets up a system of three equations and three unknowns, which you then need to solve)

We then worked on more problems. Whatever you didn't finish in class is homework.

p.263 Conceptual #6 & 12 + p.268 #70, 74, 78

Please remember that your mobiles are due next Wednesday, with next period as a work day. If you build your mobile at home and are afraid it will be destroyed in trasit to school (which OFTEN happens!) you may take a video of it that shows its sticks are straight and that all levels are free to rotate and show  or email me the video.

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. Bonus: #87

More 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) Note: the algebra at the end of the file has a mistake. This was cut out in the YouTube version.

Tomorrow you will be working on p.269 #33, 35, 39, 40. Bonus: #87. These will be due on Friday.

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 next Wednesday, 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

Torque and Equillibrium

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

Net force = 0
Net torque = 0

We did a problem together and Rotational Motion 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 25th. You will have the modular day on January 23rd or 24th to work on this in class, but that's it. I am hoping most people will only be finishing off their mobiles on that work day and will be able to turn it in right then.

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 problems. 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?
2. A young girl of mass 35 kg is 4.0 meters from the shore of a lake, standing at one end of a uniform raft of mass 90. kg and length 3.0 m. She walks along the raft away from the shore until she gets to the other end of the raft. How far is she from the shore now?

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