Spring Intro Lab

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

Spring Intro Lab

The lab is due tomorrow.

Senior Debates

It's Senior Debates day! Periods 1-4, I will not see you at all. Go directly to the auditorium and stay there, please. Period 5 and 6 will have work time, though period 5 has to take a quick survey on their phones.

Building a Mobile

Today you had the whole period to complete the Mobile Project. Leftover time was work time - remember that the take-home test is due on Thursday.

Rotational Dynamics Test

Today we took the multiple choice section of the rotational dynamics unit test, and the leftover time was work time. The free response section is a take-home test and was available for pickup on the front desk. Remember that you can use your notes and textbook on the take-home test, but other people can't help you (and other people wrote content on the internet).

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)

Fun with Angular Momentum

Today we looked at a bunch of real-life consequences of angular momentum. We 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

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

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 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 (which we'll go over tomorrow together and won't turn in) and Ch.8 (p. 270) #47 & 50 (which you need to turn in).

Angular Momentum

I am out sick again today, so I made a sort of guided notes thing: Angular Momentum. Below you will find the answers for the example problems in that guide.

Homework is 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:

Practice

I am back! But voiceless. If this had been a regular day, we would have done one problem together. Below are the problems that various periods picked last year...which ended up being all of them.

#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)

So basically today you worked on these three problem sets, with whisper help from me:

p.269 #31, 32, 33, 39
p.269 #35, 40, 87
p.263 Conceptual #6 & 12 + p.273 #70, 74, 78 (this one is new)

All of these do need to be done eventually, but I won't count any of them late, ever. I recommend figuring out how to do them before your test, though.

Combining Rotational + Linear Dynamics

I am sick again today. We would have 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:

Two years ago I was actually gone for this lecture, so here are some videos I made (thanks past me!):
Part 1: YouTube
Part 2: YouTube

Homework: p.269 #35, 40, 87. I hope to be back tomorrow, and we'll have a work day so I can help people.

Newton's 2nd Law for Rotation and Rotational Inertia

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

Notes: Torque, Angular Acceleration, and Rotational Intertia

Tonight's homework:
p. 269 #31, 32, 33, 39

You also picked up the instructions/rubric for a the Mobile Project, which you'll be doing on 1/28 or 1/29. I am giving you this early in case you want to gather special materials or start early, neither of which you actually have to do.

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 one Paragraph Length Answer problem. A video for solving the problem is here.

Homework is Ch.8 (p. 265) #8 & 21 and Rotational Motion TIPER #3

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 (email miss.volkening@gmail.com for a copy). Please turn that in.

Homework is Chapter 8 (p. 265) #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

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

Next class you will also be completing a small lab, so bring your lab notebook.