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For the Friday Webex classes, does attendance count or can we watch the lecture later?

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.

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.

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?

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.

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.

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.

Thanks!

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.

For friday's class, we're having a quiz so will we be required to turn our cameras on again?

Thanks!

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?

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?

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.

I'm always a fan of the more recent exams. Their questions seem more relevant to the course material and expectations.

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.

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.

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?

I was able to find them under the example video solutions.

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.

recent exams, the homework is way too hard.

I found it helpful to skim back through the lectures and redo every homework. Along with this you can also do example questions from the book!

I also have the same question what is the best way to study for the exam. Whether it be by past homework's or the lecture book.

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 🙂

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!

is this class curved at the end of the semester or are the percentages in the syllabus set in stone?

I think it'll be curved.

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.

Yes, I believe it is curved

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.

You know something funny? They are certainly challenging, but I feel the same way

Is there a way to check how many questions you have asked on the homework discussions without going through each homework discussion board.

You should be able to go to your account overview and then to dashboard, and you can see your comments there.

When I go to dashboard it shows recent comments, but it is the recent comments of the whole class, not my comments

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.

Is there a way to do 31A without having to consider the reactions at the joint O?

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.

I agree with John, it's easiest to slice the system apart and take the moment about the L shaped bar. This will lead you down the right path!

are any of our homework assignments dropped?

If you check the syllabus, you will see that we are given two free HW scores

2 HWs are dropped and if a significant amount of people do the course evaluation survey we get one full homework score added.

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.

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).

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?

I think that we will still have the 38 HW, my professors hasn't said anything of cancelling

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.

Anyone know when the tips will be posted for HW 33? I'm having some trouble getting started.

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.

33B

For problem 32A can we assume the pin is double sided.

As far as I know you can assume plate is double sided. assuming you meant plate instead of pin

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)?

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.

I believe that it doesn't matter. The syllabus only states that they have to be "meaningful comments" thats it.

Hi, I believe the comments just have to be meaningful and it can be either on the same or on different discussion threads

For B do we find the max stress of the two shafts individually and whichever, is higher is the max of the whole shaft?

sorry I posted this on the wrong forum

On Homework 34A where would the couple that opposes T be located? at the opposite end?

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).

Will the final exam cumulative?

If so, will it be focused on material after midterm2?

Yes, the final is cumulative. Although I am unsure where the majority of questions will come from.

Is there any way to know how many comments I have written on the blog? Or is there a way to check the log of the comments I wrote?

when finding shear force and bending moments are we going to have to draw the diagrams on the final exam?

I would assume so. It is also good practice because they give partial credit!

Yes, I think we are going to draw those diagrams. It is helpful to practice them

For the Final exam. Should we expect the exam to cover more content between exam 2 and the final, or will it be equally cumulative?

For the final how much new information will be on it?

The new information should be what we learned from exam 2 until the final. Hope this is helpful