/sci/ - Science & Math

A

>>10174627
Wrong

>>10174631
Sorry

>>10174625
None can carry any load, it's the computer screen that carries the load, you silly

B

>>10174627

>>10174632
Apparently the answer is A though and I can’t figure out why. I have a mechanical engineering degree too. I guess you would assume the load, which is distributed over the entire shelf, would be evenly distributed and therefore be right over the support? So A wouldn’t have any bending stress, but what’s the strength of that support material? How do we know the shelf can’t handle bending stress better than that support piece can handle shear?

>>10174625
A

>>10174639
B would transfer most of the load from the shelf to the support, making the support more likely to fail. A is correct because the support takes some of the load off the shelf but not all of it, and the reduced length allows it to carry more weight.

>>10174625
doesn't this depend on the material properties like compression vs. tension strength?

>>10174625
no shear strength
no yield strength
no dimensions
no loading diagram
no indication of joint types

not a lot to work with

>>10174639
with a there isn't torque on the tip of the support

>>10174646

>>10174646
Assuming a single point load on the end point. What about distributed loads, even or uneven distribution? What about single point loads at different places?
B will most likely to fail at the shelf root or at the support failing while A always spreading the load between the root and the support. The biggest load on the support at A is when the load point is in the middle but the shorter support beam means it's specific load bearing is much higher than B support's specific load bearing.

"B" puts a lot more leverage on the diagonal support. It is a longer lever and therefore puts more bending stress on the vertical piece.. I still like "B" better though. If it was real and not just a math problem: "A" would have a weakness in the screws (if it was wood) where the shelving connects to the back. If you put something heavy on the front end, you would have no support of shelf going clockwise.

>>10174684
I object. In that case leverage is 0 at the root hence no torque induced load at that point.
We need a basic CAD draw module next to TEX so us engineers can do better explanations. Maths is overrated anyways

wow, so many physics and math majors in this thread. No wonder you clueless fucks can't find a job if you can't even solve such a simple problem as this. The correct answer is you go to the person asking you to design the shelf and ask them what material they want and what the load distribution is. You fucking retards. If the material can't handle shear forces at the base then it's B. If it can't handle high compression through the support then it's A. If the weight is at the base then it's A if it's at the tip then it's B. Or any combination of those two factors. Now fuck off brainlets I said full cream not fucking onions.

Simple question, really. Imagine the beam isnt there, then they both have the same center of mass, now imagine you add only a small beam to the upper left corner, you wont change the center very much, by making it longer and shifting it to the B position you not only add weight to the construction but heavily shift its center of mass to the right, so assuming its an ideal rigid body, A will always carry more weight without falling down.

>>10174730
btw

t. physicist,

MEs and other retards who couldnt actually reason it out ITT BTFO

>>10174625
What size and shape is the load?

>>10174730
That's wrong.

>>10174625
i'd like to say B, but that smaller support on A looks tempting, and the shelf is thicker anyway so it doesn't seem like the shelf is ever going to break, so the A's smaller support would need more weight to snap than B's longer support

maybe

>>10174625
>Those hideous fucking shelves
Obviously none of you queers has ever done carpentry.

>>10174775
i'm not jesus christ

>>10174625
ITT brainlets unable to answer the question and instead trying to muddy the waters by spraying out lots of superfluous secondary questions, like a squid sprays out ink.

>>10174781
can somebody post the equations that measure the real answer and on which variables it depends?

>>10174625
You guys should learn to read questions properly. It is asked which can carry the heaviest load so all the anons talking about unkown variables need to fuck off. The question already implies that the load will be loaded so that each shelf will carry it's theoretical maximum capacity. This means that for A, all load will be put exactly onto the middle and for B all load will be on the outer edge because these are the points where each shelf will have its maximum capacity exhausted.

Because of this, A is the correct answer.

>>10174779
There has been more than one carpenter

Assuming exact same materials of construction and evenly balanced load. I would answer that B would handle more load due simply due to the placement of the brace gives it much better leverage.
Try to hold a heavy box on your shoulder and hand in the center of to bottom of the box. Then move your hand out to the end of the box and see which is easier.

>>10174807
>assuming
I'll be the one laughing when then shelf breaks and hits someones neck killing them and causing you to go to jail for negligence.
I'll laugh like this; hah, hahah, hahhuuuu, aaaaaahahaaaa, aaayyyeee lmao.

This one.

/thread

>>10174810
Nope. They're all Jesus. It's a miracle.

Assuming square cross-section on both beams (shelf and support), and same material properties;

axial compression is preferred to a bending moment (imagine a tube of paper, stronger to compress length ways than as a 'bridge')

Assuming a Uniform Distributed Load (UDL), A will have more force resolved by the support. B will have a greated bending moment on the shelf.

Under a UDL im standing underneath A. A point load, such as a hanging sign on the end, I'd take B.

t. Not autistic

>>10174969
what a shitty painting

>>10174969
What about buckling. The diagonal brace could be fixed to the beam rather than simply being pinned.

>>10174705

This. Physics & maths (under)grad genocide now.

>>10175766
FU my gay retarded 'nam vet son painted it for me

>>10175785
>what is compression
fixed or pinned its still being compressed. which is better then shear stressing as in the shelf

>>10174969
What shelf has a square cross section? It’s likely a thin board

>>10175867
Those are the support, you put the plancks on them. At least two each planck length.

>>10174625
A, only if the load is placed before the intersecting joints. Anything past that and it's better to use B
>educated guess

>>10175820
How would you do the genocide though? You can’t even count to 6 gorillion.

>>10174625
B because it creates a larger torque because of the larger distance of the beam from the wall.

>>10174625
Depends where you put the load. This is the objective answer

>>10174625
That would be your mother.

solved it, B is correct

>>10176299
Kek has a good laugh

>>10174625
A because supports take more force to buckle.

>>10176222
Wrong.
A is the only correct answer.

>>10176448
What do you mean “buckle”?

>>10176488
buck·le
/ˈbək(ə)l/
verb
gerund or present participle: buckling

2. bend and give way under pressure or strain.
"the earth buckled under the titanic stress"
synonyms: warp, bend, twist, curve, distort, contort, deform; More

>>10174639
is it maybe because the length of the bracer of A is shorter, meaning it's tensile strength holds up better?

>>10176492
Without knowing the point of application or material strength you can’t say for sure

>>10176299
niBBa u want a phd?

>>10176499
>Without knowing the point of application or material strength you can’t say for sure

The question isn't asking about the point of application or the material strength. A good engineer doesn't ask questions when faced with an easy problem because he knows what hard problems look like.

>>10176506

>>10176511
OK, You do the math and prove that there is a case where the point of application and material strength matter between A and B. I'll be here waiting when you get back with an answer that provides no value.

>>10176506
>A good engineer doesn't ask questions
this is what causes bridges to collapse and kill 20 people

>>10176516
Why dont you find one so we can see if you really are following along here

>>10176518
>when faced with an easy problem
Only reading half a sentence is what causes bridges to collapse and kill 20 people.

>>10176521
>doesn't know what buckle means
>thinks they can pretend they are the smart one
Ok...

>>10176526
Buckle doesn’t have a meaning in physics, it’s normgroid speak

>>10176528
see attached image
>>10176492

>>10176526
>only reading half a sentence
>"not paying attention to every bit of information"

in other words

>doesn't ask questions

are you trying to prove my point?

>>10176541
>I'm going to blatantly troll for (you)s by straight out ignoring what words mean and making illogical leaps.

Ok... I guess here is your (you).

>>10176476
But it's not. Stop spreading disinfo like the rest of this thread

>>10177193
why not? smaller support looks more sturdy

>>10174705
>is very smart
>doesn't directly answer question

Obviously you're right, but this is clearly supposed to be answerable as is, devoid of the qualifications you provided.

>>10174705
>If the material can't handle shear forces at the base then it's B. If it can't handle high compression through the support then it's A.
so it's A, because clearly the base is thicker than the support if you actually look at the drawing

>>10174807
This is right

>>10177205
>but this is clearly supposed to be answerable as is, devoid of the qualifications you provided.
Wtf? How do you figure that? It all depends on load distribution and member properties. The question makes no assumptions, so there are many variables missing.

>>10174625
Where do you want to place the load fuckalooo?

It seems that horizontal part will brake according to it.

>>10174835
>>10176299
this alone makes this the best thread in ages

Just think about the cross product of the radius from the point of rotation and the force applied by the support. It is larger as r gets larger so the right picture should be correct.

>>10177784
The one on the right gets less compressive stress but is more prone to buckling.

>>10174625
Brainlet here

Best I can do

>>10174625
It's A:
You have to look at the problem in terms of levers. A has the shorter leaver arm so it can hold more weight, given the same material strengths.

>>10178705
To clarify, the load you're trying to "lift" (or not lift) with the lever is the point of failure, which will be where either the horizontal or diagonal beams attach to the vertical or to eachother. A is the less efficient lever, therefore it takes more force to lift the load (i.e. more weight to break it).

>>10178705
>>10178714
Damn you're dumb

>>10178725
Go on, explain how I'm wrong. I'll wait.

>>10174625
A, draw bending moments for both it'll become obvious

>>10178731
But there are no BMs passing through B???? Because the diagonal strut means the horizontal one can't bend

>>10178730
>A is the less efficient lever, therefore it takes more force to lift the load
So there will be more force in the beam A for an equivalent load.

>>10178742
A less efficient lever is less efficient at leveraging force at the fulcrum (which I'm assuming to be the most likely point of failure for a shelf).

>>10178750
The fulcum being where the shelf meets the wall? Definitely not the case in these types of questions. It is looking for failure of the support beam.

>>10178778
Yes, because that's where the point of failure tends to be on shelves in real life. Of course it's a different matter if the question is asking about failure of the support beam.

>>10178778
In that case, would it be incorrect to assume a fulcrum in the center of the support beam (resulting in the same answer: shorter lever = stronger)?

>>10178806
>fulcrum in the center of the support beam (resulting in the same answer: shorter lever = stronger)?
Kiiiind of. Buckling failure is the most likely failure, so yeah, a shorter beam resists the buckling forces.

>>10174625
the bigger gap a girl has between her ass and her legs, the less support she gets from me

/thread

>>10178814
>fulcrum in the center of the support beam
I guess I was thinking about it this way: there'll be some sort of deformation before it snaps. As this happens, concave and convex sides form on the beam. The concave side being an area of compression around which the bending force is directed (causing the convex side to be pulled apart). I don't know if this can technically be called a fulcrum but it kind of serves the same function.
Anyways, the shorter beam being less vulnerable to buckling failure is clearly right. Just imagine breaking a stick, then trying to break one of the shorter, broken pieces.

>>10178827
>Anyways, the shorter beam being less vulnerable to buckling failure is clearly right.

Indeed, but without knowing the structure or material of the beam, we can't technically assume buckling failure. If it's a thin-walled cylindrical beam, it's possible to fail compressively before buckling. In that case B would be better since it will have less compressive forces.

>>10178846
True. It could also be made of a pressure sensitive explosive, in which case B would also be better.

>>10174625
clearly A.5, faggot