Work Day

Today you had time to work on your practice test. You will have a multiple choice quiz thing on Friday, then you will receive a take-home test for the free response section. The free response section will be due on the following Thursday (so you'll have it for 6 days).

Please continue to turn in your homework from this unit - remember that nothing from last week will be counted late since I was sick, but you do need to do that work eventually.

Here are the answers to the practice test:

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)

Rotational/Linear 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.273 #70, 74, 78

We are building mobiles next class, so bring special supplies if you wanted them.

Combining Rotational + Linear Dynamics

Today we walked through a problem that combines rotational and linear dynamics. The basic strategy goes like this:

1. Draw a free body diagram of the linear thing.
2. Write Newton's 2nd Law for the linear thing, fill in what you can.
3. Draw a free body diagram for the rotational thing with the forces drawn at the point they really are applied to the body.
4. Write Newton's 2nd Law (rotational version) for the rotational thing, fill in what you can.
5. Write (linear acceleration) = (radius)(angular acceleration) for the point where the linear and rational objects interact.
6. You should now have a system of three equations and three (or less) unknowns; solve!

Note: if there is more that one linear thing or rotational thing, you might end up with more than three equations and three unknowns. Fun!

Here is the problem we walked through:

Last year I was actually gone for this lecture, so here are some videos I made:
Part 1: YouTube
Part 2: YouTube

Homework: p.269 #35, 40, 87. Each class will pick one problem to go over together tomorrow.

More on Rotational Inertia

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

Notes: More on Rotational Inertia

Homework: p.269 #33 & 39

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

Tonight's homework:

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

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.

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)

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

Chapter 8 Practice Exam

Your exam for chapter 8 will be on Thursday. Wednesday will probably be totally eaten up by the Debates, so today is your day to study for your exam. I have a practice exam for you and I will post solutions videos tonight.

Ch. 8 Practice Exam (the formatting on the pictures is a bit messed up in Google Docs. You can also try this link)

Solutions Videos:

#4
#5
#7
#8
#9 (energy method), #9 (dynamics method)
#10
#11

Don't want to watch all of the solutions videos? I have a key with just the answers here.

Random Rotational Motion Stuff

Today we looked at a hodgepodge of things, like why cats land on their feet and how a magic trick with a ring and chain works.  Any leftover time was spent starting homework.

Homework: Ch.8 (p. 271) #58, 72, 89

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. EDIT: SEE BELOW.

Homework is Ch. 8 (p. 271) #55 (look up the mass, radius, and orbital radius of Earth with The Google), 61, 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 start that has shrunk dramatically:

One last picture with all of the equations:

Practice and Mobile Turn-In

Your mobile projects are due today! Because needed to spend most of the class taking pictures of and/or hanging up your mobiles, you spent the time 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.

You can expect a test on this unit as early as next week.

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

Cool Video From Oshadha

Oshadha found a great video that talks about using the concepts of mass and moment of inertia in toy 3D printing. Check it out!

3D Printing: the Physics of Objects

Combining Linear and Rotational Dynamics

Today we walked through a problem that required us to combine linear and rotational dynamics. Typically in these types of problems, the three equations you need are:

Net force = (mass)(linear acceleration)

Net torque = (moment of inertia)(angular acceleration)

linear acceleration = (radius)(angular acceleration)

But you need to be very careful to make sure the signs of the linear and angular accelerations match up.

We used the whiteboard, not the overhead, so I will post pictures of the completed problem when I can.
Which is 1:50 PM
The rest of the time you started working on your homework so I could help you with these new kinds of problems.

Homework: Ch.8 (p. 269) #35, 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

Homework tonight is Ch. 8 (p.269 ) #33 & 39