Logic Puzzles [FORUM GAME]

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JayKitty76
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Post by JayKitty76 » March 28th, 2019, 3:10 pm

I haven't seen anything of the sort here on LibriVox yet, so I thought I might make a thread for it. Reply here to solve mine, and/or to add one of your own. I'll start with a fairly simple one:

------------------------------------
Read this sequence, then figure out what comes next:
O T T F F S S E N
------------------------------------

Reply back here to solve, and add yours! :wink:
~Rachel
~John 3:16
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lymiewithpurpose
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Post by lymiewithpurpose » March 28th, 2019, 3:16 pm

T comes next :D. Don't have any good ones though :lol:
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Post by JayKitty76 » March 28th, 2019, 3:26 pm

lymiewithpurpose wrote:
March 28th, 2019, 3:16 pm
T comes next :D. Don't have any good ones though :lol:
Yup, that was easy, wasn't it! That's because I typed it wrong :D :lol: But here's a slightly harder one:

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A traveler comes to a fork in the road and does not know which path to take to reach his destination. There are two men at the fork, one of whom always lies while the other always tells the truth. He doesn't know which is which. He may ask one of the men only one question to find his way. What is his question and which man does he ask?
-----------------
~Rachel
~John 3:16
Want DRs? Elijah, Campbell and I have got you covered! Next DR coming soon!

lymiewithpurpose
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Post by lymiewithpurpose » March 28th, 2019, 3:31 pm

Ok, I think I've heard this one so I'll give someone else a chance to think before I say what I'm thinking.
Campbell
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SonOfTheExiles
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Post by SonOfTheExiles » March 28th, 2019, 4:15 pm

A solid cube rests on a level surface. The cube is heated by a large amount. Does the pressure the cube exerts on the surface:

A) increase?

B) remain the same?

C) decrease?

Disregard relativistic effects and stick to classical physics. Explain your reasoning.
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classicsforever
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Post by classicsforever » March 28th, 2019, 9:31 pm

-----------------
A traveler comes to a fork in the road and does not know which path to take to reach his destination. There are two men at the fork, one of whom always lies while the other always tells the truth. He doesn't know which is which. He may ask one of the men only one question to find his way. What is his question and which man does he ask?
-----------------
Wait....if he doesn't know which is which, then how could we know which man he asks? Unless that is part of the riddle... I'm terrible at these. :D
Margaret

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Post by Elizabby » March 28th, 2019, 11:52 pm

OK, I'll bite:
SonOfTheExiles wrote:
March 28th, 2019, 4:15 pm
A solid cube rests on a level surface. The cube is heated by a large amount. Does the pressure the cube exerts on the surface:
Disregard relativistic effects and stick to classical physics. Explain your reasoning.
B) remain the same

Pressure exerted by the cube is Force (F) which is equal to mass (m) multiplied by acceleration (a). F=ma

In this case acceleration is gravity which is constant.
The mass is also constant as we are told this is a solid cube, so not like heating water which might evaporate.

If mass is constant and acceleration is constant, then Force must also be constant, so B.

However, I'll be the first to admit that my classical physical classes were over 20 years ago, so don't walk under any bridges designed by me...

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Post by Availle » March 29th, 2019, 12:31 am

classicsforever wrote:
March 28th, 2019, 9:31 pm
-----------------
A traveler comes to a fork in the road and does not know which path to take to reach his destination. There are two men at the fork, one of whom always lies while the other always tells the truth. He doesn't know which is which. He may ask one of the men only one question to find his way. What is his question and which man does he ask?
-----------------
Wait....if he doesn't know which is which, then how could we know which man he asks? Unless that is part of the riddle... I'm terrible at these. :D
It doesn't matter whom he asks - if he asks the right question!

It's not difficult, but you have to be prepared to do the unexpected when receiving the answer ;-)
Cheers,
Ava.

--
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Post by SonOfTheExiles » March 29th, 2019, 12:45 am

Elizabby wrote:
March 28th, 2019, 11:52 pm
OK, I'll bite:
SonOfTheExiles wrote:
March 28th, 2019, 4:15 pm
A solid cube rests on a level surface. The cube is heated by a large amount. Does the pressure the cube exerts on the surface:
Disregard relativistic effects and stick to classical physics. Explain your reasoning.
B) remain the same

Pressure exerted by the cube is Force (F) which is equal to mass (m) multiplied by acceleration (a). F=ma

In this case acceleration is gravity which is constant.
The mass is also constant as we are told this is a solid cube, so not like heating water which might evaporate.

If mass is constant and acceleration is constant, then Force must also be constant, so B.

However, I'll be the first to admit that my classical physical classes were over 20 years ago, so don't walk under any bridges designed by me...
Everything you have said so far is correct.

But... there's always a "but", isn't there? :wink: ... the question wasn't about force. It was about pressure. Pressure = Force /Area. Do we have any reason to believe that the surface area of the face of the cube in contact with the level surface might have changed in any way?

Chris
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SonOfTheExiles
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Post by SonOfTheExiles » March 29th, 2019, 1:26 am

Textbook treatments of relativity sometimes illustrate the "equivalence principle" with the example of a person in a room with no windows. The person can not distinguish between an inertial field, caused by the room being accelerated at 1g, or a gravitational field, caused by the room sitting at rest on the Earth’s surface.

By the nature of Relativity’s equations, this equivalence principle only holds true at a point, not over any “real world” linear dimension.

Assuming very sensitive instrumentation, how might you distinguish between the inertial field of a room in an accelerating rocket, and the gravitational field of a room at rest on the Earth’s surface?

Name two ways in which the characteristics of the inertial field would differ from those of the gravitational field.

Chris
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Post by Elizabby » March 29th, 2019, 4:43 am

SonOfTheExiles wrote:
March 29th, 2019, 12:45 am
Pressure = Force /Area. Do we have any reason to believe that the surface area of the face of the cube in contact with the level surface might have changed in any way?
If the cube increases in size due to heating then there is an increase in Area.
We have already established that Force is constant since mass and acceleration/gravity are constant.
If Pressure = Force/Area, then Pressure must decrease. i.e. same weight is now spread over a larger surface.
So C.

The gravitational field question I don't think I even understand the question, so there's no way I can attempt an answer to that one!

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Post by Elizabby » March 29th, 2019, 4:58 am

JayKitty76 wrote:
March 28th, 2019, 3:26 pm
-----------------
A traveler comes to a fork in the road and does not know which path to take to reach his destination. There are two men at the fork, one of whom always lies while the other always tells the truth. He doesn't know which is which. He may ask one of the men only one question to find his way. What is his question and which man does he ask?
-----------------
This problem appears in the David Bowie movie "Labyrinth". The key is that you don't need to know which is the truth-teller and which is the liar. You just need to know the answer to the question. If there is a way of asking BOTH men in one question which is the correct path to the city, then the answer will always be a lie. The liar will lie and the truth-teller will correctly report the lie. Alternatively, the truth-teller will give the correct answer but the liar will lie about what he would have said.

So the question is: Which path would HE (the other man) tell me is the correct path to the city? Then take the other one, as this answer will be a lie.

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Post by SonOfTheExiles » March 29th, 2019, 5:23 am

Elizabby wrote:
March 29th, 2019, 4:43 am
If the cube increases in size due to heating then there is an increase in Area.
We have already established that Force is constant since mass and acceleration/gravity are constant.
If Pressure = Force/Area, then Pressure must decrease. i.e. same weight is now spread over a larger surface.
So C.
Yep, that’s it exactly!

Chris
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Post by JayKitty76 » March 29th, 2019, 4:12 pm

Wow, I'm completely lost with Chris's logic puzzle! (It's nothing against you, Chris, I'm just terrible at scientific logic!) But this is exactly the sort of puzzle I wanted, so thanks for adding that!
Elizabby wrote:
March 29th, 2019, 4:58 am
JayKitty76 wrote:
March 28th, 2019, 3:26 pm
-----------------
A traveler comes to a fork in the road and does not know which path to take to reach his destination. There are two men at the fork, one of whom always lies while the other always tells the truth. He doesn't know which is which. He may ask one of the men only one question to find his way. What is his question and which man does he ask?
-----------------
This problem appears in the David Bowie movie "Labyrinth". The key is that you don't need to know which is the truth-teller and which is the liar. You just need to know the answer to the question. If there is a way of asking BOTH men in one question which is the correct path to the city, then the answer will always be a lie. The liar will lie and the truth-teller will correctly report the lie. Alternatively, the truth-teller will give the correct answer but the liar will lie about what he would have said.

So the question is: Which path would HE (the other man) tell me is the correct path to the city? Then take the other one, as this answer will be a lie.
Yup! Specifically, and simply, the answer is:
----------------------
(Answer):
He asks either man: "If I asked your companion the way, what would he say?" Then he takes the opposite fork to the one indicated.
---------------------

So yes, exactly like Beth put it. :wink:
~Rachel
~John 3:16
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Post by SonOfTheExiles » March 29th, 2019, 5:39 pm

JayKitty76 wrote:
March 29th, 2019, 4:12 pm
Wow, I'm completely lost with Chris's logic puzzle! (It's nothing against you, Chris, I'm just terrible at scientific logic!) But this is exactly the sort of puzzle I wanted, so thanks for adding that!
The "equivalence principle": Is a person in a closed room on earth experiencing 1 gravity or in an rocket in space experiencing a constant acceleration of 1g?

As stated, this is only indistinguishable at a dimensionless point.

In three dimensional space, there are subtle, measurable differences in the stationary-on-earth (gravitational) and the accelerating-in-rocket (inertial) scenarios.

For instance... in that room inside the hollow rocket, the strength of the acceleration at the room's ceiling must be exactly the same as that at the room's floor. We know this, because if the accelerations of ceiling and floor were different, the rocket would either crumple or tear itself apart.

But what happens to Earth's gravitational field as you get further away from the Earth, as is the case of the ceiling as compared to the floor of the room?

It falls off (ie, weakens) with distance.

Once we've noticed this with our gravimeter, we can note a second difference. The "contour lines" of this suspected gravitational field will be ever so slightly curved (like the horizon from an aircraft) since the Earth is a sphere.


Cheers,
Chris


P.S. Here's another one for you....

Question: Using only a pair of scissors of unknown size, and nothing else, no measuring device or reference whatsoever .... how long is a piece of string?
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