Puzzles

[PKFFW]

1. Ok, so why is the inside of a manhole (or the sewer that it leads to for instance) also round?

2. Yip.

3. Good answer about the car. Next thing you should try is - if your call still has a oldfashion key - check which way to turn the lock to open it on the driver-side and on the passenger side. Both normally turn in opposite directions. Why is that?

Interesting suggestion about the doors of a "residence". So do all the doors of the rooms of your house open inwards?

1: Do you mean
a: Why is the sewer round
or
b: Why is the hole leading into the sewer round?

A: I may be wrong but I believe the sewer is round for two reasons. 1: It is the easiest shape to cut. Much easier to drill a round tunnel for the sewer to go in than a square one for instance. If you look at old sewers from before we had big automatic drills they are not usually round but rather sort of flat bottomed and arched over the top as that was easiest to dig. 2: Without internal supporting structure the circle is the strongest shape(at least I think it is but I may be wrong). Therefore the sewer is strongest in the shape of a circle.

B: Again, it is the easiest shape to cut. Also because it is the only shape that regardless of which way a person attempts to enter it they will always fit(well if they are going to fit at all that is). Where as with any other shape there are angles and directions in which a person would fit going through and there are angles and directions they may not fit. Lastly I believe the circle allows for the smallest total volume to be cut out whilst still ensuring that a human could fit through. Going back to my original answer too, the inside will always be a slightly smaller circle so as to ensure the lid will fit perfectly regardless of which way it is lifted into position whereas any other shape the lid must be aligned with the hole in the correct way or you risk it falling into the hole.

3: The car doors.........

My girls car still has old type locks. They turn in opposite directions. Both doors turn away from the B pillar and towards the front of the car to unlock the door and away from the front and towards the B pillar to lock the door. So Hence on the drivers side it is a clockwise turn to unlock and an anticlockwise turn to lock the door. It is opposite on the passenger side. I would guess this is to do with the way the door locking mechanism latches into the door and where it is situated, ie: on the B pillar. There would be some sort of lever in the lock that the key turns to push the actual bit of metal that locks the door into the B pillar. Hence this lever needs to be pushed towards the B pillar where the actual locking mechanism is situated.

Yes every door in my residence opens inward. Every door in every residence I have ever lived in opened inwards and every residence of friends places I have ever been to have all opened inwards. That is not to say every door of every residence in the world opens inwards. I'm sure design considerations such as space will preclude some doors from opening inwards. As a general rule though I would say most "residence" doors open inwards to the room one would be entering after opening that door. I would even say every "entry door"(ie: main entry into the residence from outside) opens inwards.

Besides the psychological reason I gave before there is one other reason I can think of. Should anything be blocking the entrance door from the outside then it is always possible for the inhabitants of the building to open the door and exit(if exit is possible at all). This would not be possible with an outward opening door in such a situation.

Chhers,
PKFFW

 

[firewalker99]

1: Do you mean
a: Why is the sewer round
or
b: Why is the hole leading into the sewer round?

Aha! Already a big step forward in your thinking :clap:

A: I may be wrong but I believe the sewer is round for two reasons. 1: It is the easiest shape to cut. Much easier to drill a round tunnel for the sewer to go in than a square one for instance. If you look at old sewers from before we had big automatic drills they are not usually round but rather sort of flat bottomed and arched over the top as that was easiest to dig. 2: Without internal supporting structure the circle is the strongest shape(at least I think it is but I may be wrong). Therefore the sewer is strongest in the shape of a circle.

I don't know about circles being the strongest structures, as far as I know triangles are. At least for construction purposes. Look at bridges, pyramids,...

B: Again, it is the easiest shape to cut. Also because it is the only shape that regardless of which way a person attempts to enter it they will always fit(well if they are going to fit at all that is). Where as with any other shape there are angles and directions in which a person would fit going through and there are angles and directions they may not fit. Lastly I believe the circle allows for the smallest total volume to be cut out whilst still ensuring that a human could fit through. Going back to my original answer too, the inside will always be a slightly smaller circle so as to ensure the lid will fit perfectly regardless of which way it is lifted into position whereas any other shape the lid must be aligned with the hole in the correct way or you risk it falling into the hole.

I think you are thinking too far... the answer is perhaps more obvious than you realize. Although you are probably right about a circle being the smallest volume to cut for humans to fit through, I should hape that designers of sewers didn't make them round for that reason. How often do people have to go down the sewer?

Anyway, have a look in your fridge or cupboard and you might be closer to the answer Not to say that MY answer is the only right one. But there are at least two reasons that are very good arguments for making manholes round instead of any other shape (square for instance).

 

[new_trader]

Aha! Already a big step forward in your thinking :clap:


I don't know about circles being the strongest structures, as far as I know triangles are. At least for construction purposes. Look at bridges, pyramids,...



I think you are thinking too far... the answer is perhaps more obvious than you realize. Although you are probably right about a circle being the smallest volume to cut for humans to fit through, I should hape that designers of sewers didn't make them round for that reason. How often do people have to go down the sewer?

Anyway, have a look in your fridge or cupboard and you might be closer to the answer Not to say that MY answer is the only right one. But there are at least two reasons that are very good arguments for making manholes round instead of any other shape (square for instance).

I'm not so sure about triangles being the strongest structure. They just become self supporting or rigid once all 3 points are connected. I think arches are theoretically the strongest structure. I suppose half a circle makes an arch...

Are you saying milk and cookies is the answer?

 

[TheBramble]

Manholes are round so that Microsoft could use the question in their psychological assessment of interviewees.

 

[firewalker99]

I'm not so sure about triangles being the strongest structure. They just become self supporting or rigid once all 3 points are connected. I think arches are theoretically the strongest structure. I suppose half a circle makes an arch...

I'll be honest, I don't have proof myself, I just know what my teachers taught me in high school. And although I usually question what teachers tell me, apparently there's a lot of consensus between engineers that a triangle is the best way to support forces as compression and tension.

Although it all depends on the purpose. A star-like building for instance will be the strongest formation to attack.

Are you saying milk and cookies is the answer?

Not really, but think of the jars you have and why all their lids are round too.
I'll give this one more day before I post the answer.

Manholes are round so that Microsoft could use the question in their psychological assessment of interviewees.

And although Microsoft might have used these questions in the past, I think there is a perfectly logical explanation for this, without one having to come up with far-fetched "out-of-the-box" answers.

 

[new_trader]

I'm not thinking of sewers anymore. But I know that having a round lid on a jar makes it easier to close and keep an airtight seal.

 

[PKFFW]

Aha! Already a big step forward in your thinking :clap:


I don't know about circles being the strongest structures, as far as I know triangles are. At least for construction purposes. Look at bridges, pyramids,...

Interconnecting triangles form very strong stuctures. A triangle on it's own is actually quite weak unless the force is applied directly to a corner. The mid point on each side has no support and must take the full application of the force if applied there.

A circle on the other hand distributes the force equally to all points within the circle, thus making it much stronger when on its own. When joined with other circles no advantage is gained as the transference of force is not possible. Therefore building large structures out of circles is not generally done unless it is an upright building.

A sewer cross section is really just a single circle. Many cross sections joined in a line make the sewer. Thus for any point where force is applied it is being applied to a circle and therefore, no matter what, that force is being applied to the "strongest" part of the structure.

I think you are thinking too far... the answer is perhaps more obvious than you realize. Although you are probably right about a circle being the smallest volume to cut for humans to fit through, I should hape that designers of sewers didn't make them round for that reason. How often do people have to go down the sewer?

Anyway, have a look in your fridge or cupboard and you might be closer to the answer Not to say that MY answer is the only right one. But there are at least two reasons that are very good arguments for making manholes round instead of any other shape (square for instance).

Not sure what you are hinting at here. Will have a think about it.

Cheers,
PKFFW

 

[firewalker99]

I'm not thinking of sewers anymore. But I know that having a round lid on a jar makes it easier to close and keep an airtight seal.

Ok, I said I would give an answer by today so here we are.

It makes it easier to close is correct, it also makes it safer to open. You can grab a round lid of a jar or a bottle cap with one hand and turn it without hurting yourself. Suppose it would've been star or triangle-shaped. You couldn't put as much force on it without one of the angles hurting your hand.

But that's not the main reason. Have you tried getting a lid in the jar? Should we be worried that a man-hole falls into the sewer? No. As the cover is round, it cannot fall in the hole. I'm surprised nobody come up with that answer more quickly. There are so many articles in our daily life where we use round lids or caps to cover things. You might not be as worried about the lid of your mayonaise falling into the jar, but having a manhole fall down the sewer... well... you get the point.

Another reason why round objects are more ergonomic, is because you can roll them over. A massive man-hole which is square cannot be moved as easily by a single handed person as a round one. I think we humans often try to construct objects in a way that will make it as easiest for us to handle. But after a while we forget why we choose to do it in that way in the first place.

Anyway, I know most of you probably will think this is useless spending time thinking about these things. Obviously man-holes aren't the most exciting point of debate. But as a departure point, it can lead to interesting discussions.

Thanks to all who have tried to answer the question.

 

[new_trader]

No. As the cover is round, it cannot fall in the hole. I'm surprised nobody come up with that answer more quickly. There are so many articles in our daily life where we use round lids or caps to cover things. You might not be as worried about the lid of your mayonaise falling into the jar, but having a manhole fall down the sewer... well... you get the point..

WHAT..!? That would have been my FIRST answer but it was already given!!

1: Do you mean
a: Why is the sewer round
or
b: Why is the hole leading into the sewer round?

A: I may be wrong but I believe the sewer is round for two reasons. 1: It is the easiest shape to cut. Much easier to drill a round tunnel for the sewer to go in than a square one for instance. If you look at old sewers from before we had big automatic drills they are not usually round but rather sort of flat bottomed and arched over the top as that was easiest to dig. 2: Without internal supporting structure the circle is the strongest shape(at least I think it is but I may be wrong). Therefore the sewer is strongest in the shape of a circle.

B: Again, it is the easiest shape to cut. Also because it is the only shape that regardless of which way a person attempts to enter it they will always fit(well if they are going to fit at all that is). Where as with any other shape there are angles and directions in which a person would fit going through and there are angles and directions they may not fit. Lastly I believe the circle allows for the smallest total volume to be cut out whilst still ensuring that a human could fit through. Going back to my original answer too, the inside will always be a slightly smaller circle so as to ensure the lid will fit perfectly regardless of which way it is lifted into position whereas any other shape the lid must be aligned with the hole in the correct way or you risk it falling into the hole.
3: The car doors.........

My girls car still has old type locks. They turn in opposite directions. Both doors turn away from the B pillar and towards the front of the car to unlock the door and away from the front and towards the B pillar to lock the door. So Hence on the drivers side it is a clockwise turn to unlock and an anticlockwise turn to lock the door. It is opposite on the passenger side. I would guess this is to do with the way the door locking mechanism latches into the door and where it is situated, ie: on the B pillar. There would be some sort of lever in the lock that the key turns to push the actual bit of metal that locks the door into the B pillar. Hence this lever needs to be pushed towards the B pillar where the actual locking mechanism is situated.

Yes every door in my residence opens inward. Every door in every residence I have ever lived in opened inwards and every residence of friends places I have ever been to have all opened inwards. That is not to say every door of every residence in the world opens inwards. I'm sure design considerations such as space will preclude some doors from opening inwards. As a general rule though I would say most "residence" doors open inwards to the room one would be entering after opening that door. I would even say every "entry door"(ie: main entry into the residence from outside) opens inwards.

Besides the psychological reason I gave before there is one other reason I can think of. Should anything be blocking the entrance door from the outside then it is always possible for the inhabitants of the building to open the door and exit(if exit is possible at all). This would not be possible with an outward opening door in such a situation.

Chhers,
PKFFW

 

[firewalker99]

WHAT..!? That would have been my FIRST answer but it was already given!!

Uh-oh. Looks like I clearly overlooked that one. Apologies to you and PKFFW. Seriously, must have been looking at the screen for too long nline2lo

You know what, you can ask me a question now in return

Anyway, no harm done, I belief you if you say that was the first thing you would've answered. Next to that, there's still the second reason I mentioned.

 

[JTrader]

Puzzles.COM Home

 

[PKFFW]

......But that's not the main reason. Have you tried getting a lid in the jar? Should we be worried that a man-hole falls into the sewer? No. As the cover is round, it cannot fall in the hole. I'm surprised nobody come up with that answer more quickly. There are so many articles in our daily life where we use round lids or caps to cover things. You might not be as worried about the lid of your mayonaise falling into the jar, but having a manhole fall down the sewer... well... you get the point.

As new_trader pointed out......my original answer was.........

1: A circle is the only shape where the manhole lid will never be able to fall into the manhole.

Cheers,
PKFFW

 

[new_trader]

On a wall are 3 standard on/off switches. One (and only one) controls a light bulb inside a light-tight, well-insulated closet. The other two switches do nothing. You can only open the closet door once, and cannot touch/change any switches after the door is open (or re-closed, for that matter). Damaging or disassembling the door, walls, or switches is against the rules.

Within these constraints, can you determine with certainty which switch controls the light bulb?

 

[firewalker99]

On a wall are 3 standard on/off switches. One (and only one) controls a light bulb inside a light-tight, well-insulated closet. The other two switches do nothing. You can only open the closet door once, and cannot touch/change any switches after the door is open (or re-closed, for that matter). Damaging or disassembling the door, walls, or switches is against the rules.

Within these constraints, can you determine with certainty which switch controls the light bulb?

Do you know anything about these switches? Whether they are placed in parallel are in series? Or do they each control the light bulb separately (meaning there's only one switch that turns the light on ànd off)?

To be honest I don't think you can determine it with certainty, because you cannot touch a switch after the door is open. If I'm wrong, please let me know than I will continue and will not stop until I've found out how it can be done

 

[firewalker99]

On a wall are 3 standard on/off switches. One (and only one) controls a light bulb inside a light-tight, well-insulated closet. The other two switches do nothing. You can only open the closet door once, and cannot touch/change any switches after the door is open (or re-closed, for that matter). Damaging or disassembling the door, walls, or switches is against the rules.

Within these constraints, can you determine with certainty which switch controls the light bulb?

First attempt at thinking out-of-the-box:

You ask help of another person which opens/closes the closet :?:

 

[new_trader]

Do you know anything about these switches? Whether they are placed in parallel are in series? Or do they each control the light bulb separately (meaning there's only one switch that turns the light on ànd off)?

To be honest I don't think you can determine it with certainty, because you cannot touch a switch after the door is open. If I'm wrong, please let me know than I will continue and will not stop until I've found out how it can be done

There is no trick or combination with the switches at all. Only 1 switch is electrically connected to the light bulb such that current will flow and illuminate the bulb when the circuit is closed by 1 and only 1 switch. The other two switches are dummy switches. They have no wires connected to them at all.

 

[new_trader]

First attempt at thinking out-of-the-box:

You ask help of another person which opens/closes the closet :?:

It can be done without any assistance. The closet door can only be opened AFTER any of the switches have been touched. You can't touch any of the switches once the door has been opened, and you only get 1 turn to open it. You can't leave it open and operate any of the switches.

 

[firewalker99]

It can be done without any assistance. The closet door can only be opened AFTER any of the switches have been touched. You can't touch any of the switches once the door has been opened, and you only get 1 turn to open it. You can't leave it open and operate any of the switches.

Yes! I think I've found it. I just posted "I think I found it" but had to delete the answer because I realized I was wrong.

But now I'm pretty convinced I'm right. Don't want to spoil the fun for others by posting my answer. I will PM you the answer. If I'm right, well than this truly is a very good puzzle new_trader. Really like the thought process I observed on my own. Now just hope I'm right

 

[senyorqueso]

Test the switches one by one to see which make your electicity meter start going faster, then leave that one on and open the door? Unless the meter's in the same cupboard as the light.

 

[new_trader]

Test the switches one by one to see which make your electicity meter start going faster, then leave that one on and open the door? Unless the meter's in the same cupboard as the light.

In your case, the 2 dummy switches are electrically connected to a dummy load which draws the same current as the light bulb.