141 Fall 2018 Week 10

Wow, last week of classes. We will review material while exploring new questions. Additionally, we will add trigonometry and you will be allowed to use the two kinematic formulas that most classes introduce in the first week of classes, now that you are able to solve questions without these formulas.

FINAL EXAM: Information is posted under Exam Week at the end of the timeline table on main class website.


Before Class

        • Hopefully, you’ve sent me the description and url of your video. Details were Emailed to you Thursday evening and posted at the end of Week 9 timeline.
        • Solutions to BE! #7 posted on main class website.
        • Please see: Big Picture Rotation Video that includes precession. It was assigned just before MT#2. It is a good thing to see again, now that we’ve covered angular momentum as a vector.
        • PS#10 Solutions posted. Please see them and understand how to do them.
        • PS#11 posted – due this Thursday.
        • See video on Fuzzy Dice
        • Watch this video: Spinning Skater What are the forces on a skater’s arms when she is spinning very fast?
        • Please see some old problems Solving flywheel with hanging mass This video is from winter quarter, 2016 so the problem number is different.
        • Extra Credit? No. sorry. Following some of your comments, I found a statement in the trigonometry video stating that there’s extra credit for not using a calculator. … feeling of embarrassment… Uh, no, that’s a very old statement and is not correct. I’ve replaced the statement with the following: “Now we’ve introduced trigonometry and can use it on the final and on homework. However, you can also just draw a triangle as correctly as possible and estimate ratios, as we have been doing. I find it more important that we consider the magnitude of components before we start to jam numbers in to a black box (even if your calculator is a different color). This is why we introduced trig so late.” I apologize for the confusion.

In Class:

Hand in PS#10

Shoot Money out of Tree

After Class
This week, you will be asked to fill out two surveys/evaluations for this class. One comes to you via Email (I think) from the university.
The other I have made to help me better understand your experience in the class and better serve future students.


        • Solving the Ladder Problem, this is from winter quarter 2016, so the number of the problem is different
        • See a video from last quarter regarding trebuchet.
        • Also see this from BurningMan
        • See Firehose Video
        • Please consider shooting a monkey out of a tree… but also warm up by solving the problem I put on the presentation Monday: Exercise 6, in section 7.6. I’ve added it to your problem set #11.
        • If you haven’t already, please fill out the course survey I made to help me understand your experience in the class. Please do the survey, and I’ll bring cookies to the final exam!
        • Please fill out the university’s student evaluations that were Emailed to you.
        • Please listen to this song about laying bricks… if you like. I was wrong about the mistake the singer made… listen if you like.

In Class
Hand in your final version of project #1.
Falling off a ladder.

Bring your bike to class day!!
first hour
Before Class

        • Surveys: Please take the university survey for this class. The link was sent to you via Email.
        • Bicycle Transmission,
        • See video from your colleagues Toy Car Catapult
        • Solutions for PS#9 posted, Solutions for PS#10 posted
        • Please see assigned videos for Tuesday if you didn’t get to see them already. I’ve made the deadline Friday (tomorrow).
        • Hey in doing the last question on PS#10, remember that the disks were at a radius of 20 cm from the center of the spinning wheel, and moved 60 cm horizontally as they fell 110 cm to the floor. Also remember that the slide when the surface was inclined about 20 degrees with respect to the horizontal.
        • If you haven’t already, please fill out the course survey I made to help me understand your experience in the class.
        • Please fill out the university’s evaluations of this course.
        • Do problem #1 on the problem set.

In Class:

        • Bring your bike to class day! we explore bicycle transmission.
        • Hand in your corrections for project #2. This could be in a form of a new video or a written document.

After Class

Thursday: Wow… our last class.
Before Class

          • See video on solution for 2D inelastic collision from a problem set from years past.
          • Bucket of Water over your Head
          • #1 Spring Energy Conversion from the Midterms corrections.
          • If you haven’t already, please fill out the course survey I made to help me understand your experience in the class.
          • please also fill out the university’s evaluations of this course. The last day to do this is tomorrow.
          • I’ll post the class responses for both evaluations for you to read as soon as I get them, so please make sure your voice is heard.
          • Please consider which string breaks first when I pull downward on a string attached to the heavy ball hanging on another string.
          • We calculated the coefficient of friction of the felt-covered wooden block and the steel surface of the rotating platform two different ways:
          • 1) We tipped the platform until the block slid. It happened at about an angle of 35 degrees.
          • 2) We put the block on the edge of the wheel and rotated it faster and faster until the block slipped off and hit the ground. The important measurements here are:
              • Height of the platform: 108 cm
              • Horizontal distance traveled from platform edge while falling: 70 cm
              • Radius that the block was spinning: 18 cm
          • Using these data, please calculate the coefficient of friction both ways. Are the two values pretty close?… within experimental uncertainty?
        • In-Class¬†FINAL EXAM:
          In our classroom as indicated on the main class website