So I was doing this question and here is my working out
time period (P`) is 86401/86400 . Normal period is 1. Therefore, we can infer that
EDIT: Picture doesn't seem to work but I calculate "L" by rearranging it and I get 0.253...... metres
So we now need to find to delta L
EDIT2: ^^^^ Delta L ^^^^
which when divided by that constant, alpha, does NOT lead to the right answer!
Any ideas?

DrSebWilkes
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 23102017 19:12
Last edited by DrSebWilkes; 23102017 at 19:17. 
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 24102017 11:38
Okay fine fine no one is coming forward ... how are you SUPPOSED to do it then? Maybe then we can see if I am wrong by comparison?

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 25102017 15:48
Tagged the most helpful guy I know ... plz help
Tagged: 
KMan_PhysCheM
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 25102017 15:59
(Original post by DrSebWilkes)
Tagged the most helpful guy I know ... plz help
However, having plugged numbers into my calculator, I disagree with your numbers.
Typing by my calculator.
However, without the previous bits of the question, I wouldn't know whether or not this is right. 
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 25102017 16:05
(Original post by DrSebWilkes)
Tagged the most helpful guy I know ... plz help(Original post by KMan_PhysCheM)
It would be useful if you posted the preamble (assuming there is one) and the beginning of the question, since there is some theory that I'm not familiar with.
However, having plugged numbers into my calculator, I disagree with your numbers.
Typing by my calculator.
However, without the previous bits of the question, I wouldn't know whether or not this is right. 
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 25102017 16:10
(Original post by KMan_PhysCheM)
It would be useful if you posted the preamble (assuming there is one) and the beginning of the question, since there is some theory that I'm not familiar with.
However, having plugged numbers into my calculator, I disagree with your numbers.
Typing by my calculator.
However, without the previous bits of the question, I wouldn't know whether or not this is right.
So basically, what I did was find the "new" time period, and then found out the length of that new time period, and subtracted away from it the old "orignal" length; this delta L is divided by the constant in the question to give the maximum delta Temperature. 
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 25102017 16:12
(Original post by DrSebWilkes)
So I was doing this question and here is my working out
time period (P`) is 86401/86400 . Normal period is 1. Therefore, we can infer that
EDIT: Picture doesn't seem to work but I calculate "L" by rearranging it and I get 0.253...... metres
So we now need to find to delta L
EDIT2: ^^^^ Delta L ^^^^
which when divided by that constant, alpha, does NOT lead to the right answer!
Any ideas?
Let be the time period, since will be used for temperature.
If the temperature is increased by , then the length will increase by , since we are told is the fractional increase in length.
For an expanded pendulum at a higher temperature:
Now,
After some algebra, you can write in terms of .
Now, for it to be accurate to within one second in one day, the ratio must be equal to the ratio of one second to one day.
This will then allow you to solve for using your previous resultLast edited by KMan_PhysCheM; 25102017 at 16:15. 
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 25102017 16:14
(Original post by DrSebWilkes)
There was, but it effectively just gave a more complicated version of the pendulum formula that isn't needed for this bit.
So basically, what I did was find the "new" time period, and then found out the length of that new time period, and subtracted away from it the old "orignal" length; this delta L is divided by the constant in the question to give the maximum delta Temperature. 
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 25102017 16:20
(Original post by KMan_PhysCheM)
Okay, well as you probably know, I don't like numbers. I've worked it through now (I think; I don't actually have the official answers!) and given the start of the workings in my previous post.
I don't see anything wrong with how you do it, but I don't see how it differs either? You L+kL could just be equal to some constant "C".
so we have time period P` which equals "stuff" * Root C and P which is stuff * Root L, and in both cases it's easy to rearrange each function to find C (or L) in terms of P
And so if we have a value for both C and L, then the difference in length is just CL ...
Tell me I'm not going crazy! 
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 25102017 16:33
(Original post by DrSebWilkes)
Yeah no that's pretty similar to how the "markscheme" did it but this was a calculator paper so I used it.
I don't see anything wrong with how you do it, but I don't see how it differs either? You L+kL could just be equal to some constant "C".
so we have time period P` which equals "stuff" * Root C and P which is stuff * Root L, and in both cases it's easy to rearrange each function to find C (or L) in terms of P
And so if we have a value for both C and L, then the difference in length is just CL ...
Tell me I'm not going crazy! 
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 25102017 16:35
(Original post by KMan_PhysCheM)
How do you get your values for C and L? 
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 25102017 16:42
(Original post by DrSebWilkes)
Well "L" is mentioned above, and for "C", exactly the same method but with P`=86401/86400 (if thought your clock was right and counted 86400 counts in a day, it'd still be accurate to the required time)
So your method for finding C is invalid, as far as I can see... 
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 25102017 16:46
(Original post by KMan_PhysCheM)
Okay...
So your method for finding C is invalid, as far as I can see...
And if that's what P` is equal to then I should be able to find "C" just like I found L 
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 25102017 16:49
(Original post by DrSebWilkes)
But P = 1 so = P`
And if that's what P` is equal to then I should be able to find "C" just like I found L
Pretty much every pendulum clock I've seen has a period of 2 seconds... (it ticks every time the bob swings to one side). 
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 25102017 16:54
(Original post by KMan_PhysCheM)
Sorry, I didn't clockit before, but why do you suppose P=1?
Pretty much every pendulum clock I've seen has a period of 2 seconds... (it ticks every time the bob swings to one side).
Still ... now you bring this to my attention I do see that your method seems to be less assumptiony which is good. I think the take home message, regardless, is that the fewer assumptions the better and in this case. Hmm I think, I guess, this was just going to be one of those questions that wasn't inherently compatible with me : 
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 26102017 11:36
(Original post by DrSebWilkes)
So I was doing this question and here is my working out
time period (P`) is 86401/86400 . Normal period is 1. Therefore, we can infer that
EDIT: Picture doesn't seem to work but I calculate "L" by rearranging it and I get 0.253...... metres
So we now need to find to delta L
EDIT2: ^^^^ Delta L ^^^^
which when divided by that constant, alpha, does NOT lead to the right answer!
Any ideas?
You may want to check your algebra. 
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 26102017 23:04
(Original post by Eimmanuel)
I am not sure what have you done to get the "wrong answer". I can get the same answer based on your method and the method proposed by KMan_PhysCheM.
You may want to check your algebra. 
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 31102017 10:03
(Original post by Eimmanuel)
I am not sure what have you done to get the "wrong answer". I can get the same answer based on your method and the method proposed by KMan_PhysCheM.
You may want to check your algebra. 
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 31102017 11:59
(Original post by DrSebWilkes)
So I was doing this question and here is my working out
time period (P`) is 86401/86400 . Normal period is 1. Therefore, we can infer that
EDIT: Picture doesn't seem to work but I calculate "L" by rearranging it and I get 0.253...... metres
So we now need to find to delta L
EDIT2: ^^^^ Delta L ^^^^
which when divided by that constant, alpha, does NOT lead to the right answer!
Any ideas?(Original post by DrSebWilkes)
I forgot about this and now I just remembered! So I put into wolfram alpha, and it spat out the exact same answer as what I wrote above showing it's wrong. So what on earth am I doing wrong then?!
As I mentioned I did not know what had you done to get the wrong answer.
Based on your method, L is already known ( and T = 1 s)
If you manipulate the above expression correctly, you will get
From this, you should get δT as 1.2 K. 
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 31102017 12:36
(Original post by Eimmanuel)
<snip>
Thanks for the help so far! (You have restored some confidence I had lost :O )
EDIT: I can confirm that if I solve it as "L+kL" I get the right answer ....
and when I divide my "x" by L, I get the right answer ... euughh ... so that means the "x" isn't an absolute change but a ratio? Well thanks for pointing me in the right direction.Last edited by DrSebWilkes; 31102017 at 12:45.
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