test job interview

[exxon]

What does this have to do with the thread?

If you want to flood what was written with another tide, do it as well: who puts us back is the forum, not me. who will judge are others, not me.

 

[meccanicamg]

What does this have to do with the thread?

If you want to flood what was written with another tide, do it as well: who puts us back is the forum, not me. who will judge are others, not me.

It's not a tide of anything else. and how. you have a preloaded rope and weight attacks us and is equal to having an additional weight and weight.

You think they don't add up. The shots are summed up and I'm making you an un abstract real example.

There is no preload if you don't put a force on it.
Let's see. .

 

[exxon]

You think they don't add up. the shots are summed up. .

What do you want me to say? You're part of those who said "no." and as I said before, quiet, you are in abundant company.

 

[meccanicamg]

What do you want me to say? You're part of those who said "no." and as I said before, quiet, you are in abundant company.

I don't mind because reality is different from an unrealistic assumption. There is a difference between "break" and "do not break".

 

[PaoloColombani]

beautiful discussion, just before going to bed is good for sleep!

@ mechanicsmg
the shots do not add up, although it is very easy to deceive. try to imagine adding gradually load to the plate; only achieved 2 n of weight strength, equal exactly the tension that holds the bat pressed to the fixed support, zeroing the force with which it presses on the support. from there, increasing the load (c > 20 n) begins the detachment of the plate from the support. but as long as tension and load are not equal, the traction force of the rope is always equal to its tensioning force: it is the fundamental concept of precarious.

@ exxon
if you assume that the thread is inextensible, enter the hypothesis of the rigid body, with infinite rigidity. It would not be conceptually possible to apply an internal tension to a rigid body for which elastic behavior would be required. I don't know if the candidate who responded that the case is undetermined, had taken this consideration.

 

[meccanicamg]

the fact is that 2 n should not be added to 10 kg to get the load. once the load is applied (which must exceed 2 n to create a detachment, and therefore a further stretch of the wire) it is only the latter to stretch the wire, for 98 n. this because the support is fixed and rigid. between an applied load of 0 n and 2 n the wire does not see any load difference
has been one of the hardest rocks to understand at times of construction of machines, is the same case of the tightened screw

I'll be hard to understand, but I don't agree at all. If he has zero preload he has all 100n to attack. if it is preloaded of 2n it remains 98n then it breaks.
But if it is unextensible it does not stretch...so it never detaches and therefore becomes infinitely robust and yields only with load that tends to infinite.
Something rough.

a screw mounted with no preload can withstand a traction force due to the external load higher than the screw preloaded to 80% of the yield.

If instead we want to use the friction plates surely to slip the faces I have to apply a separation force equal to the precarious and then still a little. but the stem of the vine hears all the strength of the precarious that I have won and of the additional force (the little).

we have some samples on m24 and m30 vines in this regard and if it were true that I precarious to death and then my vine resists 100% we would have invented the perpetual motion, that therefore there are convient people who exist, there is not for now.

 

[meccanicamg]

beautiful discussion, just before going to bed is good for sleep!

@ mechanicsmg
the shots do not add up, although it is very easy to deceive. try to imagine adding load by hand to the piattello, only achieved the 2 n of weight strength, equals exactly the tension that holds the bat pressed to the fixed support, eliminating the force with which it presses on the support. from there, increasing the load (c > 20 n) begins the detachment of the plate from the support. but as long as tension and load are not equal, the traction force of the rope is always equal to its tensioning force: it is the fundamental concept of precarious.

I can't see it as you say.
a force that is precarious or not gets it with a weight application.

you tell me that:
If you have given 2n somehow to stretch and place the bat, you have 2n and the bat does not flow horizontally.
then you attach to the piattello an increasing weight that subtracts to the 2n to give the stress to the wire because you need 2n to get to download the piattello from the plate and then 98n useful you lower again. But I'm a poor thread, it's 100n because those 2ns were pulling the thread.

Yet it does not come back because I have already used part of its load capacity and the residual is reduced.

with the hard wire there is no story.... what does it stretch? k•x is not....

 

[Onda]

when I apply the 10kg i.e. 98.1 n the wire is separated from the plate, so the initial pretension 2ns disappear and the wire only sees the 98.1 n applied and therefore does not break.
As long as I apply a force lower than pretension the wire does not see load increase, I simply am moving the load from the tied plate interface to the applied load. when the load passes the pretension, the wire sees an increase of load and is "forgettable" of the pretension.

 

[cacciatorino]

when I apply the 10kg i.e. 98.1 n the wire is separated from the plate, so the initial pretension 2ns disappear and the wire only sees the 98.1 n applied and therefore does not break.
As long as I apply a force lower than pretension the wire does not see load increase, I simply am moving the load from the tied plate interface to the applied load. when the load passes the pretension, the wire sees an increase of load and is "forgettable" of the pretension.

We all agree here. The problem is that the text of the specific exercise that the thread is inextensible.

 

[Onda]

I probably read the question wrong. I considered the elastic thread, so my answer is correct in that case. with the inextensible thread, you actually do not download the pretension, so I am not convinced of the answer. but I am not convinced that an answer is possible because it is not possible to give a pretension to an inextricable thing. because to give a pretension I have to give a move, if it is all inextensible as I move of an infinitesimal the loads go infinitely.
I said that. since the wire is inextensible, considering that it already has 2n of strength and that applying the load does not discharge its pretension, because precisely inextensible, when the load with 98.1n the wire sees 100.1 total and breaks

 

[ale_.93]

who answered no, don't brash: she's in thick company... this can be a good opportunity to learn something that even if simple, is not so obvious. the right answer is obviously "yes".

of the six candidates, one did not answer, suggesting that the problem had no solution (????), the other five responded all "no".

yesterday, a couple of candidates had a general preparation more than discreet and I would expect the correct answer, instead no. I am a little relieved to see that here, many answered "yes". Of course every answer is influenced by the previous ones, but I opened the thread with the fear of not finding any gave the right answer.

for those who answered "no" and had doubts, observe the image below.
View attachment 53186the tension in the wire is given by the spring elongated by its rest position that just generate the 2 n.

Now, you think you're attacking the piattello a mass of 0.1 kg.

- Did something move?
- The spring exercises the same strength?
- Has the tension in the wire changed?

comparing these findings with the assumptions used for responding "no", it will probably understand the error.

I would have answered no. your reasoning is correct but the text explicitly says that it is a thread inestensibile So I thought I didn't model him with a spring. Am I right?

 

[Cristallo]

I ask vein in advance to the engineers, but from the bottom of my preparation (I am completing the course for access to geometra help), mechanics says something that escapes you and cannot make you understand.
initial conditions (even if specified after the query):
point or fixed, fixed point f, preloaded wire of 2n -> shift in point o=0.00 shift point s = 0.00, axial voltage in up 2n, instead we call it with its -2n sign (although declared after)
load condition -> Applial 98,07n to the plate:
the points are fixed and do not move the piattello si (theoretical but canceled by the unextensibility of the wire), from which it comes that:load to the plate level: +98,07 + (-2,00n)= 96,07nvoltage wire interior: +98,07 + 2,00n = 100.07n ->beyond the guaranteed resistance
even in the case of the interposition of the spring the speech is worth: in the stretch between the point or and the spring the tension in the wire is always worth 98,07+2,00 and therefore out specific.

However, I repeat, this is the point of view of one who is just beginning to understand how forces work, moments etc.

 

[stevie]

I'll add my...

the problem is poor place, the initial conditions are contradictory and incongruent.
At first we talk about inextensible wire, pretended between two fixed supports?
physically it is something impossible. Pretension means applying an initial force in order to achieve an initial state. which means that initially the thread was not perfectly straight, in order to understand it had divergences due to an initial precompression situation.
let's say then that with those 2 n I have exceeded the initial tensions of the cable that starting from a slight precompression situation now lies completely relaxed with internal actions null...certain if so it would be able to support the next 10 kg, the problem is that the cable initially is defined unextensible therefore more than to a cable you should think of a tie that is loaded (traction) of 2 n and then later of other 98.1 n.
not by chance after having defined inextensible the thread subsequently in giving the explanation idealizes as a spring...which physically is less unextensible exists, indeed it is the model of elasticity par excellence.

sincerely all the speech seems to me a bit of a supercazzola with triple scappellamento on the left.. .

 

[stevie]

the only sensible answer was "the problem has no solution"

 

[ceschi1959]

We imagine an rod between two fixed distance walls that is cooled by a quantity such that an internal voltage (traction) of 2n is generated and therefore we are in the case exposed by exxon. We then heat the rod so as to have a voltage (compression in this case) of 98,06 n. there is no shift.
I remember an exercise similar to construction science.... in the second half of the last century by now

 

[Cristallo]

We imagine an rod between two fixed distance walls that is cooled by a quantity such that an internal voltage (traction) of 2n is generated and therefore we are in the case exposed by exxon. We then heat the rod so as to have a voltage (compression in this case) of 98,06 n. there is no shift.
I remember an exercise similar to construction science.... in the second half of the last century by now

You are right in the example you carry, but we get out of the conditions of the question as a place. in many ways.
the pillar is free to move and is not confined by the two walls, so you will not have mai the condition of switching from a traction to a compression, in the examination rod.
then it is not an auction but a thread for which, by definition, in a wire you cannot have compression.
born as traction and traction remains also after the application of the load.
If I want to follow your example, I should say cool the element until I have 2n of tension, then I cool it again to add another 98.06n, what would you get?
the core of the matter lies in less 2, condition guaranteed excluding the presence of the plate s and the type of bond of the plate (unidirectional).
I repeat, it is correct to say that at the piattello there will be 98-2 newton, but it is equally correct to say that just after the bat there will be 98+2 newton.

It almost seems like a guy looking in the sky puts the fingertips in front of the moon, whispers and thinks: I've got a lot of fat, I've got my thumb as much as the moon now.
But I remembered that these menades were doing in the middle to joke, I didn't think they could be the subject of intake tests. ...

 

[haga78]

when I apply the 10kg i.e. 98.1 n the wire is separated from the plate, so the initial pretension 2ns disappear and the wire only sees the 98.1 n applied and therefore does not break.
As long as I apply a force lower than pretension the wire does not see load increase, I simply am moving the load from the tied plate interface to the applied load. when the load passes the pretension, the wire sees an increase of load and is "forgettable" of the pretension.

Yeah, I sang, too.

I probably read the question wrong. I considered the elastic thread, so my answer is correct in that case. with the inextensible thread, you actually do not download the pretension, so I am not convinced of the answer. but I am not convinced that an answer is possible because it is not possible to give a pretension to an inextricable thing. because to give a pretension I have to give a move, if it is all inextensible as I move of an infinitesimal the loads go infinitely.
I said that. since the wire is inextensible, considering that it already has 2n of strength and that applying the load does not discharge its pretension, because precisely inextensible, when the load with 98.1n the wire sees 100.1 total and breaks

I'll add my...

the problem is poor place, the initial conditions are contradictory and incongruent.
At first we talk about inextensible wire, pretended between two fixed supports?
physically it is something impossible. Pretension means applying an initial force in order to achieve an initial state. which means that initially the thread was not perfectly straight, in order to understand it had divergences due to an initial precompression situation.
let's say then that with those 2 n I have exceeded the initial tensions of the cable that starting from a slight precompression situation now lies completely relaxed with internal actions null...certain if so it would be able to support the next 10 kg, the problem is that the cable initially is defined unextensible therefore more than to a cable you should think of a tie that is loaded (traction) of 2 n and then later of other 98.1 n.
not by chance after having defined inextensible the thread subsequently in giving the explanation idealizes as a spring...which physically is less unextensible exists, indeed it is the model of elasticity par excellence.

sincerely all the speech seems to me a bit of a supercazzola with triple scappellamento on the left.. .

the setting is misleading.

the only sensible answer was "the problem has no solution"

at the end perhaps it was the only one who was right, confirming that the essay is the one who knows not to know
exxon knows that at this point you have to hire him:

 

[meccanicamg]

Fortunately that they are decades that you make the warmed tirants, mounted warm and also pretensed with known couple and the total axial load is the elastothermic and pure elastic return of the additional couple.

 

[PaoloColombani]

but the internal tension of the rod (or the reaction it causes on the constraints) also in this case is always given by its elastic response to the rest condition, which would be the condition of the untied rod. In fact, if you lose the auction, it has its extension of balance, that is a precise extension for a precise temperature. at the end is always the elastic property of the body that provides tension. No?

 

[cacciatorino]

but the internal tension of the rod (or the reaction it causes on the constraints) also in this case is always given by its elastic response to the rest condition, which would be the condition of the untied rod. In fact, if you lose the auction, it has its extension of balance, that is a precise extension for a precise temperature. at the end is always the elastic property of the body that provides tension. No?

there was an initial definition error between those who spoke of tension (forces per unit of surface) when it meant the effort (a total value applied to the element intended in its interest). then the rest made it the definition of "unextensible" that makes the problem unreal. I would never submit a candidate to a trick test like this. I miss that quality should come out, if the ability to reason, to tell the boss that he said nonsense, to find a solution to an unresolvable problem, boh?