Physics Help: Proving Elevator Problem Not Our Fault

[sophiecentaur]

I am trying to defend the laws of physics,

The laws of physics are not in question. The lift design is almost certainly quite adequate to deal with some very high stresses and I don't think anyone is suggesting that these young miscreants were in any danger at all or that significant material damage was done.
My issue is with the 'laws of' behaviour and the assumption that these lads couldn't be expected to restrain themselves without specific training or notices (or a nearby figure of authority). One of the purposes of a school is to regulate behaviour (it seems that many parents do not assume that responsibility any more) and the sort of negative feedback that the school dished out was quite in order. There is no telling what inconvenience they caused by taking the lift out of action. Should no one have taken any punitive action? Is it ok to accept that "kids do that sort of thing"?

 

[Danger]

Is it ok to accept that "kids do that sort of thing"?

Well to start with, I never saw a mention of their ages anywhere. I assumed them to be university students rather than "kids". (Alright, we're both older than dirt so they're kids to us, but not in the eyes of society.)
Given that, have you considered that these "kids" knew that their behaviour wouldn't have any effect upon a certified elevator and thus had no malice in mind?

 

[A.T.]

Should no one have taken any punitive action?

Hyperbole-man strikes again. The issue was financial responsibility, not "any punitive action". I don't see grounds for financial responsibility, if they were first-time offenders and not explicitly informed about the elevators sensibilities.

 

[Danger]

The issue was financial responsibility, not "any punitive action".

Thanks for that. I was about to edit my last post to add that fact, but it's nice that you got in ahead of me.

 

[vivesdn]

If you came to a stop in 3 mm after a 30 cm drop then you would experience at least 30cm/3mm = 100 g's (9800 m/s²) of peak acceleration.

I think that space does not relate with time lineally. So 3mm would not be 100g's but 30g's. Said that, 3mm was only an assumption to note that tension on a steel cable can be much higer that just body weight. And of course, the guys did not behave as solid rods as you point out. But note that you do not need 30g's to be out of the maximum load, but less that 5g's.

As for rock climbing: a 10m fall (quite normal by the way) on a steel line and you would prefer to be free falling.

 

[sophiecentaur]

Hyperbole-man strikes again. The issue was financial responsibility, not "any punitive action". I don't see grounds for financial responsibility, if they were first-time offenders and not explicitly informed about the elevators sensibilities.

Do you have any experience of dealing with 'kids' (of any age)?
Do you not know that young people can often be thoughtless and mindless. If there had been no repercussions about what they did then what would make them modify their behaviour next time? Perhaps when they are 20kg more massive, a lot stronger and when there are more of them. they might actually do some damage. But you don't seriously suggest it was a legit 'experiment', do you? They were just 'messing' around where they would have known they shouldn't have.
Is the idea of 'punishment' not to be allowed any more? Just how liberal are you?

 

[Travis_King]

A.T.:
If these guys had been jumping into aisles at the library to test the merits of lever action, and several rows of book shelves fell down causing some amount of damage, would you have the same opinion? Nobody expressely forbid them from jumping into bookshelves, afterall.

I'm still young, so maybe that's "clouding my judgement" a bit. I know that these situations suck. There was most likely no malice intended, just a bit of harmless fun. I hope they get out of any charges, but:

1) Physics won't help
2) If their horseplay did indeed cause damage then they are liable for that damage.
(Danger, obviously they didn't snap any cables, but safety systems cost money to be reset. A large jolt caused by three normal sized people jumping, might just make the sensors say "Whoah! what was that!" and do its thing.)

We still don't know what exactly the school said they damaged, though, so really we're all just speculating as to possible circumstances.

 

[Danger]

(Danger, obviously they didn't snap any cables, but safety systems cost money to be reset. A large jolt caused by three normal sized people jumping, might just make the sensors say "Whoah! what was that!" and do its thing.)

And I acknowledged in an earlier post that I can understand if that expense is what they are being held liable for. The original post, however, specified that they are being accused of breaking the machine. I still maintain that such is not physically possible. In any event, it's totally illegal for anyone but a licensed elevator inspector to put a dormant elevator back into operation. Since the OP said that the school has "fixed" the lift, there will be the inspector's report stating exactly what went wrong and why. S/he should be the final authority as to who is at fault.

 

[Travis_King]

Yup on that last point. Agreed.

 

[CraigAllan]

Whey you say "break", what exactly did break?

Its an elastic system and to break the ropes and motor you'd have to create a momentary tension in the ropes of about ten times their stated capacity. I can't believe its possible with three little humans jumping. Just the car dangling on the end of the ropes in which you jumped has a mass of over a ton. Jumping won't accelerate the car enough to bother the ropes much.

More likely you cracked the floor, which is likely mere inch thick plywood supported on a steel angle bar grid.

 

[Danger]

More likely you cracked the floor, which is likely mere inch thick plywood supported on a steel angle bar grid.

You've just inspired me to launch a previously unthought-of terrorist attack: releasing termites in elevators...

 

[sophiecentaur]

Almost as good as pouring mercury all over an aeroplane floor.

 

[Danger]

Almost as good as pouring mercury all over an aeroplane floor.

I rather suspect that yours might be deemed a tad more antisocial than mine...

 

[sophiecentaur]

Two old hooligans, then.