A test of your common sense

Not enough information.If the beam is flexible it would simply bend between the two endpoints and eventually squeeze past them. If the two end points aren't fixed, they'd be forced out sideways as some of the downward force became lateral by the bending of the beam.If the beam is not perfectly rigid and the two endoints are uncrushable and imoveable, the beam would break at either or both points b & c as the beam flexes down or mid centre between a & b depending on the amount of bending the beam allows itself (ie if if deforms into an arc)Assuming a rigid beam and fixed and uncrushable end points, the beam could fail at any point though an unevenness or weakness in it's structure.Assuming a perfectly uniform and rigid beam with fixed and uncrushable end points points (was this your meaning?) then I'm not sure. I would guess near to or at A as both downward pressures would be exerted evenly between a & b but there would be a penetrating force at A combined with pressure at a point.

Um, what has common sense got to do with it?It's an engineering question using engineering language. You're asking people that think, not to think. In my opinion, thinking IS using common sense. Relying only on common sense is a last resort equivalent to saying "I don't know but my E. coli tell me......."If I ever need to remind myself of that, I go read something rediculous about quantum theory - or the law.Edited by Tangle, : No reason given.

You mean look at it but don't think about it? I really don't have that kind of talent.

There's nothing wrong with the assumed premise that common sense can't always be used to solve problems. It's obvious that some questions require extensive education/research before the questions can even be understood.I think your example was too much of a technical question to work for you. Probabilities are a better way of messing with people's minds because they often seem simple, but sometimes aren't.Several well known counter intuitive puzzles also demonstrate that 'common sense' can't be relied on. This is the Monty Hall puzzleSuppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1 [but the door is not opened], and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?If you haven't seen the puzzle before, it seems simple enough but it makes most people's head hurt.(Answer here, but do try to work it out first Monty Hall problem - Wikipedia)Here's a less well known one:
Someone deals you a bridge hand (13 cards from a regular deck of 52 cards). You look at the hand and notice you have an Ace and say I have an Ace. What is the probability that you have another Ace?The cards are collected and different hand is dealt. This time you look at your hand and state I have the Ace of Spades (which is true), what is the probability, this time, that you have another Ace?Question: Is the probability in the second case the same as before, a lower probability, or a higher probability?

With a totally rigid beam, fixed at both ends, with no inherrant weaknesses, it breaks at either or both the fixed points of a & d.

I heard a psychologist on the radio last month who's written a whole book around this question. (Cognitive bias actually, but you know what I mean).A bat and ball cost a dollar and ten cents.
The bat costs a dollar more than the ball.
How much does the ball cost?Wish I could remember his name because he had some interesting things to say.

Yes, I've seen that one...even knowing the trick, I still have to puzzle over it for a minute or two.Here's the answer to the cards: Clear? I'm not.

Yes, that's correct. It's not a trick or a hard question, but the majority of people asked it will say 10 cents. THAT'S why you can't rely on common sense - people have cognitive bias.Cognitive bias - Wikipedia

Don't shoot the messenger...

Edited!Taz,I think by now it's pretty clear that lots of us felt the question didn't do quite what you intended it to do.I totally agree with the premise though, I just think that the actual example caused us too many problems for you to demonstrate it properly.Or maybe we're just a bunch of nick-picking, pedantic, argumentative tossers. (Actually, it's not an either or choice ;-)Anyhoo - what's the bloody answer?!Edited by Tangle, : wrong suspect arrested

Bugger, you're right - I'll delete.

The bloody answer!Edited by Tangle, : No reason given.

You see, when some of us gave you the "well it depends" answer which gave the circumstances when it would fail in each of those places, we were accused of 'over thinking the problem'. Now the answer turns out to depend on those exact same assumptions.I really do think you picked the wrong audience.

Very young children can understand 2+2=4, but not usually Calculus until they are older and have learned more.Children can understand the simple concepts of evolution - that small changes that are beneficial to organisms will be selected for in their environment and carried on by their offspring - but will probably never understand the molecular biology that underpins it unless they go on to specialise in that field of study.I understand the principles behind bridge building but I could not even attempt to generate the maths necessary to actually design one - we leave that job to those whose life's work is to do it.Uneducated individuals not understanding the intricate detail of everything, does not negate the facts that bridges carry loads and are successfully built, calculus works and evolution happens. Thinking that everyone needs to understand everything or that everything needs to be common sense for it to be true or to work would be silly wouldn't it?Edited by Tangle, : No reason given.

I'm prepared to put a large bet on the fact that Taz will tell you that you're wrong to say that I'm not qualified to discuss evolution. Are you prepared to take it?