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Re: Bullet Weight - Logic Problem for everyone...
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Please tell me how this scenario would work in either [2] was heavy or [5] was light.




Hey DKing, I'll try my best. I'll use as much of the above example as possible so as not to confuse things.

...


This is for if [2] is Heavy.

Now we go back and look at the First Comparison which was set up as follows back in Part 1:

[1] [2] [3] [4] ^ {5} {6} {7} {8}

But, this time the Scale is "NOT" Balanced. That will mean the "different" Bullet is in:

[1] [2] [3] [4] ^ {5} {6} {7} {8}

Since the Right side of the Scale goes Up then [1] [2] [3] [4] is Heavy or {5} {6} {7} {8} is Light.< !--color--> And, we know for sure that <9> <10> <11> <12> are all alike.

For the Second Comparison set it up as follows:

[1] [2] {5} <9> ^ [3] [4] <10> <11>

Now the Right side of the Scale goes Up, and we know that either [1] or [2] must be Heavy because [3] & [4] are on the Right Side and they were on the side that went Down in the First Comparison. We also know {5} can't be heavy because of the First Comparison. And <9> <10> <11> are already known to be alike from the First Comparison.

Now the Third Comparison:

[1] ^ [2] would tell me which one is Heavy.

...

This is for if {5}is Light.

Now we go back and look at the First Comparison which was set up as follows back in Part 1:

[1] [2] [3] [4] ^ {5} {6} {7} {8}

But, this time the Scale is "NOT" Balanced. That will mean the "different" Bullet is in:

[1] [2] [3] [4] ^ {5} {6} {7} {8}

The Right side of the Scale goes Up so [1] [2] [3] [4] is Heavy or {5} {6} {7} {8} is Light.< !--color--> And, we know for sure that <9> <10> <11> <12> are all alike.

For the Second Comparison set it up as follows:

[1] [2] {5} <9> ^ [3] [4] <10> <11>

Now the Right side of the Scale goes Down, and we know that either [3] or [4] "might be" Heavy because [1] & [2] are on the other side and they were on the side that went Down in the First Comparison. We also know {5} "might be" Light because it was on the Side that went Up in both the First Comparison and Second Comparison. And <9> <10> <11> are already known to be alike from the First Comparison.

Now the Third Comparison:

[3] ^ [4] would tell me if one of them is Heavy.

If they Balance then {5} is Light.

...

Hey DKing, Did that help?
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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You guys all blew it. you dont need to weigh any of them on the scale. load all bullets into equal brass and powders. shoot all through a chrony. the one that goes the fastest is the lightest, or the slowest is the heaviest. And I did not touch your darn scale once.





Nice theory that would work in the standard deviation was zero for bullets of exactly the same weight.Unfortunately this is not the case so the theory is faulty.
 
Posts: 3104 | Location: alberta,canada | Registered: 28 January 2002Reply With Quote
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Hey DKing, No problem at all. It is good to have a System Challenged to see if it can stand up to the Pressure.

By the way, the above even works with 168gr Sierra MatchKings.
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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Okay

Looks good to me, thanks for the clarification. Must be a bad biorythm day for me
 
Posts: 226 | Location: Dorchester County, South Carolina U.S.A. | Registered: 15 December 2003Reply With Quote
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If you thought that was easy try this one:

< !--color--> If a brick weighs one pound and half a brick.

What does a brick and a half weigh.

< !--color--> < !--color--> Frank
 
Posts: 53 | Location: Bundaberg,Queensland , Australia | Registered: 10 October 2002Reply With Quote
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For a definitive answer in 2 weighings:

1. Balance 5 vs 5 arranged vertically in both pans moving, say, the right set to the right to achieve balance. From the position of the right set, you now know the weight by which one bullet on either side is high or low. You also know that IF the left side contains the error, it is heavy and if the right side contains the error, it is light.

(if they balance on center, the culpret is on of the two bullets set aside and these can be simply balanced against any of the known 165 grainters to determine heavy or light in an alternate and definitive step 2.)

2. Since you now know that the two unweighted bullets are each 165 grs, you can position the 5 vs 5 sets horizontally on center, add one of the known 165 grainers to each side on center, and slide both sets of 5 in or out to achieve a second state of balance. If you moved them together to achieve balance you know that the error was heavy, and apart indicates light. Remember, although you are moving 10 bullets by equal amounts, only one is changing the balance. From #1 above, this tells you which set of 5 is heavy or light, and you already know by how much. Given these known facts, and the position of the 2 reference bullets, there is one and only one bullet that is the culpret.
 
Posts: 1111 | Location: Afton, VA | Registered: 31 May 2003Reply With Quote
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Hey Sabot, The Scale is an "Assayor's Scale" style with the Pans suspended from 3-chains on each Pan. In this style scale, the relative position of the item(s) on the Pan is un-important.

...

Are you visualizing the Scale built like a Teter-Toter or See-Saw? Interesting idea!

Here is the problem as I see it in your method. When you originally place the 10 Bullets Vertically with 5 on each side of the Scale in the center, that is the First Comparison. Then "each adjustment" you make in attempt to achieve a Balance counts as another Comparison:

Quote:

moving, say, the right set to the right to achieve balance.




If you were able to move the 5 on the Right side to the Right slightly and realized you achieved Balance, that "was" the Second Comparison. (Or, it may take more adjustments and each one is a Comparison.)

But, giving your method the benefit of the doubt, lets say you did get it Balanced on the above Second Comparison. Now you have 5 on the Right that "may" have a Light Bullet, or you "may" have a Heavy Bullet in the 5 on the Left.

How do you determine which one it is and if it is Heavier or Lighter for absolutely sure with one additional Comparison?

...

In the original post, I didn't mention how much the Bullets actually weigh, just that one is Heavier and one is Lighter. I only mentioned about the 168gr Sierra MatchKings to "DKing" because I believe he is a MatchKing fan. But they have no real bearing on the original problem. Sure didn't mean to confuse the issue any more than it already is.

Outstanding attempt though. Do you agree with what I just posted, or did I misunderstand your post?
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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This is a very old Logic Problem from one of my Professors when I was in school. I've modified it slightly to be of interest to those of us who Reload.

...

You have a Balance Beam Scale which has a 6" diameter Pan on each side.

And you have 12 - 0.308" 165gr Bullets which look as if they are all exactly the same. Eleven of them have the EXACT same weight and one is either slightly heavier or lighter.

The difference in weight can not be felt. You do not have access to any other objects of a known weight.

What is the minimum number of weighings it takes to know for absolute certainty which Bullet is different and if it is heavier or lighter?

...

It took me 30 minutes just to remember the Problem. If you do figure it out, I'll encourage you to hold onto the way to do it until everyone else that expresses an interest in "thinking through it" has responded, but do respond with the number of weighings it took you.

Best of luck to you folks.




Sorry, you said "balance beam scale", and the teeter totter type qualifies Also, when one weighs, say, a powder charge for the first time you are seeking a state of balance, and when you achieve that by moving the weights that is "one weighing".

How about a poll asking for a vote on whether I got the right answer given the problem as stated?
 
Posts: 1111 | Location: Afton, VA | Registered: 31 May 2003Reply With Quote
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... Hey AC, ...It seems that I accidentally mis-lead you though. ... We really aren't "weighing" the Bullets. It is a "Comparison Scale" - a pan on each side - like the old scales in the Assayor's Office...






Hey Sabot, This was on page 2 in a response to AC. Not arguing with you though. No problem at all from me about the "Poll". Have at it.



Totally forgot about mentioning 165gr Bullets. Thanks for pointing that out. But, the actual weight is irrelevant, just that 11 are alike and "1" is different - either heavier or lighter



...



OK, let's say you did "guess accurately" and got the See-Saw Scale Balanced on the First Comparison. You now know that one of the 5 Bullets on the Right "might be" Light or that one of the 5 Bullets on the Left "might be" Heavy. And you have 2 Bullets off to the side that are now known to be alike.



How do you isolate to the exact Bullet that is different and know for sure it is Heavier or Lighter in "1 Comparison"? You said you could do it in 2 Comparisons at the most.



And no, you can't slide Bullets around on the See-Saw Pan and see what happens without counting each re-positioning as a "Comparison".
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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Hey Sabot, I've given your method some thought overnight and am impressed with the "concept" of the See-Saw Style Scale.

Have you ever seen a commercial one? Did it have special Weights for the Standard(s)? Did it have some kind of Graduated Positioning Lines on each pan?

I've never seen one, but that doesn't mean they don't exist. Very interesting.

...

Also thought about your saying that sliding the bullets around on the Pans should "not" count as a Comparison, or do I have that wrong?

If they don't count, then why not put 6 on each side aligned Vertically at the center and then slide each bullet out individually until you determine which one is different? Since that would not count as a "Comparison", if I understand you correctly, then you could do it with " 0 " Comparisons.

...

I fully support your offer to take a "Poll" on the method you have. I don't agree with it, but I will admit it is a very interesting concept.
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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I thought about sliding them out one at a time with 6/6 centered, but in my mind this is a "trial and error" approach and would definitely violate your rules as stated in your original post. In my mind, when you slide all of them together to achieve a state of balance, you are doing the same thing as you are finding the balance point on a powder scale, i.e., making one measurement.

Most chemistry labs will have several types of scales and one of them will be a balance beam with two flat pans situated above the beam. They also have a second hinged support arm to each pan that allows it to remain flat as it rises and falls. If you disable the support arm, this scale is sensitive to position since there is no plumb line effect to center the mass under a fixed point on the balance beam.

You can make the suspended type scale reveal its sensitivity to position by observing theamount that the suspended pan swings to achieve center...like a plumb line...when the weighed mass is placed off center.

Now, whether these observations can be made accurately with no other tools is an issue I can't argue. In concept, and on paper it would work. As a practical matter, I doubt we could determine the weight discrepancy of one bullet with enough accuracy to find the culpret in a line up!
 
Posts: 1111 | Location: Afton, VA | Registered: 31 May 2003Reply With Quote
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Hey Sabot, I am familiar with the 2-"hinged" pan Scales, but never looked at one closely enough to see how they were made in the non-visible portion behind the Frame. Thanks for the description.

If I bring up this Logic Problem in the future, I'll have to be more specific about the Scale in the very beginning.

Excellent thinking on your part concerning a "way" to reach a solution.

Best of luck to you.
 
Posts: 9920 | Location: Carolinas, USA | Registered: 22 April 2001Reply With Quote
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Hot Core -

Thanks for an excellent problem. A lot of folks enjoyed it. A lot of us reload just because it is fun to TRY and solve problems. I do concede that my response fell into a grey area, since I made the less than defendable assumption that we could accurately assess weight with only the tools we had. I think that if it were only a 1 grain difference, it could not be done with the method I arrived at. One would probably need a laser or something to get it right...or even make a good guess
 
Posts: 1111 | Location: Afton, VA | Registered: 31 May 2003Reply With Quote
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