Members Definition and 164 Threads

This year the member awards will be a couple of weeks later than usual. We'll start voting for two weeks the week of the new year and the ceremony mid-Jan 2025. For now, take a look back at last year https://www.physicsforums.com/threads/2023-member-award-ceremony.1058856/

Please select up to 3 members who tickle your funny bone the most here at PF in 2023. Oftentimes comedy is the perfect companion to science! This is a popular vote. Polls were created by weighing activity levels in comedic threads and positive reactions. Everyone nominated should feel honored...

Please select up to 3 members who were most impactful in the academic and career guidance forums in 2023. This is a popular vote. Polls were created by weighing activity and measure of helpfulness. Everyone nominated should feel honored. Many more could be added to this poll, we can never...

Hoping someone can chip in and help me understand a problem when it comes to two-force members. I have a structure as shown below. Essentially its a single body attached at 3 points with pin joints. My question is, is it appropriate to treat each of the left and right side as individual...

Hi guys, this is an exercise I have been tasked to solve for an assignment. First of explaining you what I have done to solve it using the shear equation, in order to find the maximum shear stress and the shear flow in the juncture, one big question: how is it legal to utilize the shear formula...

Hello! I am new to mechanics of materials and I am very confused about the problem below. So the shear formula is: tau = VQ/It From the book (Hibbeler) I understand that Q is "y'A', where A' is the cross-sectional area of the segment that is connected to the beam at the juncture where the...

Merry Christmas PF members! Thanks everyone for another interesting and fun year! And thanks to @Greg Bernhardt for keeping the forum alive! (especially during these trying times we have lived, and are living, with the corona virus)

Hello everyone, I have a friend who serves in the military, he enlisted right out of high school (about 3 years ago) and he is looking to start a program to earn his bachelors degree. Due to his current role in the military, he needs to take courses online in order to fulfill his duties. He...

Hello: I was reading about thin-walled members under shear force, specifically example 7-7 of Hibbeler's Engineering Mechanics, Mechanics of Materials. First, the fourth Edition: As you can see above. He starts by computing the moment of inertia on the first equation by subtracting a rectangle...

Sometimes I see a line (or maybe a brief multiline) post or part of a post in the Physics Forums that I think is pithy, witty, and maybe acerbically funny. I invite other members to post accordingly. I'll start with a few recent ones: Well, the 3rd law is a bit problematic in relativity...

Since the question only asked for one member, I was trying to solve it using method of section. I cut in the middle of BD. I was unable to solve it because it has 4 unknown. Then I looked at the solution, it say that CD is zero force member. I don’t understand why CD is zero force member. Could...

This truss is supposed to have 4 zero force members and i have picked the following. Does it look right? Left side: Join has 2 members of which the colinear are the 2 vertical members and so the horizontal must be 0 Right side: Join has 2 members with no external load, therefore both are 0 I am...

As a follow-up to a previous thread I started about % of white Americans with colonial roots, I thought I'd pose the following question below, about whether any of you (American or Canadian PF members), as far as you know, have roots in what is now Canada or the US dating back to the 17th or...

i mean why is my brother physically different then me. why aren't we twins by default? don't we have the same chromosomes inhererented from our parents? aren't zygotes the same from the start? dumb question prolly, but i do not have the answer. are chromosomes copied with errors or something...

is T=2*q*A formuala valid for both open thin-walled and closed thin-walled members, where T is torque, q is shear flow, and A is the Area.

Homework Statement How many combinations of people are there if you choose 4 or 5 from a group of 10? Homework Equations Relies on binomials The Attempt at a Solution binomial (10,4) = binomial (10,6) = 210 But when choosing 5 the answer is binomial (10,5) / 2 = 126 Why do I need to divide by 2?

Hi everyone! First of all I want to congratulate @Orodruin for his book publication! I myself thought that maybe someday, I would like to write a book. So I became a little bit curious about other titles that may have been written by Physicsforum members. I hear Benjamin Crowell is also a member...

Homework Statement I'm trying to solve for this problem below.How would you be able to get the force in member ID and GC? Find the reaction forces in member AFGH Homework Equations ∑M = 0 ∑[F][/y] = 0 ∑[F][/x] = 0[/B] The Attempt at a Solution I dismembered all of its parts but no matter...

I am a Computer Science major - I am unfortunately in a group where the other two members are lazy, and I end up doing most of the work. It's too late to change groups. The class itself consists of a research paper/presentations, as well as a programming project/app. Every time I clearly tell...

Anything of neme (or is it meme??) type quality. This one regarding off topic posts is as subtle as a brick: Thanks Professor N.

Find x and y if x, y are members of real numbers and: (x+i)(3-iy)=1+13i I first expanded it to give: 3x-yix+3i+y=1+13i Then I equaled 3x+y=1 and -yx+3=13 But afterwards I do other steps and get the wrong answer.

HAPPY NEW YEAR PF FORUM May this year brings joyful and happiness to all of us. And may new discoveries for the good of humanity comes up.

My professor explained to us that the purpose of a zero-force member in a truss is to increase the stability of the truss during construction, to provide added support if the loading is changed and to prevent the structure from becoming a mechanism. It is this latter point that I do not...

Homework Statement In the notes , I don't understand that flange is thin , and the top and bottom surface are free of stress , can someone help to explain please? Secondly , why the q' is assumed to be q ' throughout the flange is assumed to be 0 ? why are they stress free ? We could see that...

In a council vote for a proposal, there a nine council members. There is a 60% chance that each council person will vote in favour of the proposal. What is then likelihood that the proposal will pass? So, this means that 5 or greater members must vote in favour. These are independent events...

Homework Statement Find force in members EA, EF and EG given the loads shown. A and G are pinned supports. Homework Equations Three equations of equilibrium for sections (method of sections) 2 equations for any node (method of joints). I also used the dimensions to decompose member forces. The...

Homework Statement For a larger project we had to redesign a truss to prevent certain members going beyond yield stress. I've found that due to the nature of the reaction forces and the supports used, the only way to do this is to introduce an X-brace in the bay nearest the supports (as well...

https://drive.google.com/file/d/0B39n6QfDU8f3SE9nUHhHckRIRFE/view?usp=sharing https://drive.google.com/file/d/0B39n6QfDU8f3SE9nUHhHckRIRFE/view?usp=sharing 1. Homework Statement I am not sure about the concept of zero-forced members. There are forces applied on the members, why are they...

I have seen poems about MHB , so now this is the time to compose a poem about it's members. So here is it, (Tongueout) There's a site called Mathhelpboards, Math loving members are always on board (Tongueout) Evgeny is a master on geometry MarkFl is a king on trigonometry (Tongueout)...

Hi all! I was just wondering what hobbies/interests do you have other than academia? I've always wanted to learn to play a music instrument and lately I've taken a liking to classical music, been thinking about signing up for violin classes.

Drakkith has already initiated a post on this, but I wanted to ask this again: How do you visualise a PF member when you interact with them? Do you see them as their avatars? What if they don't have one? Do you visualise them by their names? What if their names and avatars collide (like mine...

Homework Statement We are given this frame and asked to find the forces at C, D, E and F. Distance from D to E is 16 feet. Distance from C to D is 8 feet; distance from E to F is also 8 feet. Distance from A to D is 6 feet; distance from D to G also 6 feet.[/B]Homework EquationsThe Attempt...

Homework Statement Determine the components of the forces acting on each member of the pin-connected frame shown. (the frame shown is drawn as a free-body diagram in the image provided below (the top-most portion) and is correct) Homework Equations Equilibrium equations: ∑M=0 ∑Fx=0 ∑Fy=0 The...

Homework Statement Okay, I need help quick, exam in few hours, I won't be able to reply to this later. http://puu.sh/lQeXl/42907b0a12.jpg In my lectures notes this is given. In the example shown with it, the one on the right in particular. Look at Joint C, it is unloaded, it also has to...

Homework Statement Is this correct? The sum of the forces in the Y have to be zero and there is only two y-components so it's pretty simple to determine this. There are also only two x-components so those will also cancel each other out as they have to go in opposite directions to balance as...

Hi everyone! I am a new member. :)

I was wondering how members CL and JE are zero members? They both have forces applied to them, so why would it be zero? The attached image is the solution.

Homework Statement I am given the forces on picture and I´m asked to find the reactions on both supports. I see they are pin supports so they ask me for 4 unknowns. Homework Equations Sum of forces in both directions equal to zero Sum of torques wrt a convenient point equal to zero THREE...

Homework Statement Dont really need the answer, but I want to know if point C has Cx and Cy or just Cy. I am confused there.

http://imgur.com/lPIRaie 1. What are the Zero force members in this truss? 2. Is the truss internally statically determinate? Im not too sure what question 2 is but I would guess yes? Many thanks~

Homework Statement Member BC exerts on Member AC a force P directed along line knowing that P must have a 325 N horizontal component, determine (a) the magnitude of the force P, Homework Equations Trig I suppose The Attempt at a Solution So I'm not sure if this correct I found two angles...

Homework Statement When a force of 2 lb is applied to the handles of the brad squeezer, it pulls in the smooth rod AB. Determine the force P exerted on each of the smooth brads at C and D Homework Equations ##\sum F_x=0## ##\sum M=0## ##\sum F_y=0## The Attempt at a Solution I drew a free...

The website on the main page on the lower right will tell you the staff that is on, and some of the members, along with that it tells you how many guests and how many "ghosts" are these just random computers that have left Physics Forums open in another tab? (Something I have been guilty of many...

The question tells us that a tensile force of 80kN acts upon the thin rod and hence we know there will be an equal but opposite force on the other side. However, I don't understand why there are compressive forces on the tube? We aren't told about this in the question. Thanks

Homework Statement Show that the members of the Lie algebra of SO(n) are anti-symmetric nxn matrices. To start, assume that the nxn orthogonal matrix R which is an element of SO(n) depends on a single parameter t. Then differentiate the expression: R.RT= I with respect to the parameter t...

I was just googling something which led me to an old PF thread, i saw a few awarded members like @hootnany, @Kurdt, @Njorl @Enigma and many more.I don't see them around, What happened to them?? PS I'm sorry if i included someone who actually is still around(i haven't)

Can anyone please explain where does 5/sqrt29 and 3/sqrt34 come from? I already got BC/know how to find BC, but in my own method, I tried to use moment about A or B, knowing that there is HGx, HGy & HCy, HCx -- there are way too many unknowns @ H. So, looking at this, I'm wondering where does...

Hello everyone, I'm attempting to come up with a way to calculate the most efficient 7 members truss layout using Scilab. The assignment is to make a highway sign support. It has to be L shaped and the truss system is only for the top horizontal part. Two supports. The sign is hanging at the...

I need help calculating the size of the wood members I need in my truss. I understand the basics; I first need to calculate the load, then the stress on each member, then pick a wooden member which has that stress with a safety factor of let's say 2.0. The reason why I want to perform the...

Homework Statement Homework EquationsThe Attempt at a Solution Was trying to solve for the horizontal reaction at B. Why is BC a two-force member but not AE?