65 thoughts on “General discussion threads”

  1. For HW 6A, I recall from previous physics classes that the moment/torque equation can be set up by a de facto rotation of the force vector so that it is perpendicular to the distance arm d (essentially finding the force vector component perpendicular to d). From a cursory inspection however, this answer would be different from the method recommended in the book and from TAs (what I understand to be the 'correct' answer, which is finding the the perpendicular component of the distance arm--in this case this only includes the variable L, not b). Intuitively, these answers look like they should be identical. Like I said, I have not investigated this apparent discrepancy thoroughly, but if anyone has any thoughts on the matter I'd be intrigued to hear them.

  2. Hi there. Does anyone know why the reaction force A in the example from Wednesday's lecture has no x component? I'd appreciate some clarification, as he didn't even include it in the beginning of the problem. How'd he know its zero?

    My professor is Jim Jones, by the way.

  3. Is there an easy way to make the screen larger on the Kaltura live streams for lectures with Professor Vasconcelos? Also, will I be able to do the lecture quizzes if I was watching a live stream?

    1. There's certain options within the livestream, if you click in the upper right hand corner there's 3 orientation options, the completely filled in square works best for me. I had similar issues at first. Now I find volume to be the bigger issue.

    2. Luke, you can either use your phone on the QR code, or what I do is click on the quiz link that is given on our course homepage in brightspace. That will take you to the same screen, and is what I have been using.

  4. Hi,
    Are the exams cumulative? Just wanted to know if I should focus on really understanding the new information for the next exam or if I should spend my time reviewing what I got wrong on the last exam.


    1. I would say it is good to review the basics and have a general understanding of the material, but I do not believe the exams are cumulative, but having a good foundation can't hurt.

  5. For HW 20A, I used the moments about the arm and the fx and fy equations about the wedge along with the friction equations and it appears that I still have too many unknowns to solve for with the equations. In addition to this, I set up the problem how Krousgil did in his lecture and I am concerned that the friction force should oppose the N2 in the opposite direction that he depicted. Does anyone have any suggestions?

  6. One of the assumptions we need to make with truss problems is that loads are applied at the joints of two-force elements. Can those loads be represented as line loads?

  7. Has anyone found a couple of the provided exam 2 practice exams to be particularly useful compared to the other ones? I want to know which ones I should start with.

      1. I agree, the expectations are clear on the type of questions and how they will be formatted. Also give you a way to focus on the things that you might not quite understand fully.

  8. Does anyone know where Murphy's lecture 17 is from this morning? I tried looking in Brightspace and I don't think it's been updated yet. I just wanted to make sure I'm looking in the right place.

  9. I do not know if this has already been brought up but for the belt friction section exercises 6.D.2, 6.D.3, and 6.D.5 the wrong links have been attached. Is there anywhere where I could find those videos?

  10. Is it more useful to study the recent exams and hw's, or the lecturebook examples? I found from the previous exam that the lecturebook examples did not help much. I'm wondering if I should put some of my time into looking at the examples.

    1. Hey Robert! For me personally, I found that going over past homework and old exams proved to be very beneficial. I would also suggest focusing on understanding the concepts and general approaches to how to solve problems rather than just memorizing how to do specific problems. I think this will help you gain a better general understanding of the concepts covered which will allow you apply that knowledge to a broad array of problems! Make sure to also review the mistakes you may have made in old homework and quizzes so you don't make those mistakes again ­čÖé

    2. what worked for me was studying the past exams and understanding how to solve them. Also, studying the homework and understanding the concepts will help you a lot. And most importantly use the TA office hours! Whenever there's a problem you don't understand instead of just memorizing how to solve it try to go to the office hours and asking them about it!

    1. I do not think anyone will know until the end of semester. I beliebe they are going to decide on the curve after looking at the final overall grades of everyone in the class.

  11. Is it weird that I've been finding the homework problems a little bit fun? Sometimes they feel a bit like puzzles to me, and I usually feel really satisfied after I finish a problem.

  12. On stress and strain problems, are there any scenarios where it would help to section off a certain segment to analyze the axial load, or does it not matter which side you analyze after making a section.

    1. I found that it was best to split the system into its members and take the moment equation on the L shaped member only. If you take this moment at O, you should be able to find the force H in the y dimension without having to account for the reactions at joint O.

  13. In Brightspace it says we have 36 lessons but on the blog it only shows up to 33 homeworks. Do we only have 33 assignments or will those be posted in the future.

    1. Hi Salim, under the "Hwk Problem Statements" section of the blog there are now 38 homework assignments listed (only those up to homework 32 are available to view for now).

  14. Are there still going to be 38 homeworks? According to the course schedule we are 1 behind. Are we cancelling one or going to have an extra one due at some point?

  15. For HW 32 problem B, how to we know if the member loads are in tension or compression? I currently have that members 1 and 2 are in compression and member 3 is in tension. Not sure if this is what anyone else is getting after their calculations.

  16. For 33A you wanna cut the shaft into 4 sections, and show the tension in each area. From there, use sum of moments to find the unknowns in terms of T. Then use the shear stress formula stress = Tp/J to solve for each section.


  17. So about the blog comment points, do I have to write 8 different comments on 8 different homework or it does not matter? Like can I write two comments on one hw (for example two comments on HW1.A)?

    1. Hi Eddy. From the way I understand that wording in the syllabus, it seems like the posts don't have to be limited to the homework discussions. In addition, It just says "8 meaningful comments." It does not say that you can't post multiple comments on a homework. It may be better to check with a TA but this is how I
      see it.

    1. For a reaction couple to exist, the system in question must be fixed somewhere. If a torque to the system is applied in this scenario, and the fixed point is able to resist twisting in the direction of the applied torque, then there is a reaction couple at the fixed point(s).

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