Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    3
    ReputationRep:
    I am absolutely flummoxed by this question. if anyone could just tell me the right representations i'm sure i could solve it, but i just don't understand the wording at all. [apologies, i'm no use with LaTeX]

    "If you visit the mediaeval Great Hall, at the top of the high street in Winchester, just 20 minutes by car/train north of Southampton, you will see a circular table, 18 foot in diameter, that is claimed to be King Arthur's round table. If Arthur did really exist, it is most likely that he was a local chieftain in the dark ages with poor written records immediately following the Roman withdrawal in the 5th century AD." (which i'm pretty sure is all completely irrelevant)
    "The table was recorded as having been in Winchester in 1484, but it was not known how old it really was. In 1976 the Council had it carbon-dated. The decay rate of Carbon-14 to Carbon-12 atoms is 1.245 x 10^-4 per year. The number of radioactive Carbon-14 atoms decayng was measured to be
    dN/dt = -6.08
    per minute per gramme. In living wood the decay rate is 6.68 particles per minute per gramme. Work out how old the table is and hence deduce whether this could be Arthur's round table?"

    Thanks VERY much for any help
    Offline

    1
    ReputationRep:
    The rate given 1.245x10^-4 per year tells you that after one year 1-1.245x10^-4 of the original C14 remains.

    That's 0.999875 or 99.9875%

    Current level = original x 0.999875^years

    Changing to base e

    Current level = original x e^(-0.000125 * years)

    Any use?
    • Thread Starter
    Offline

    3
    ReputationRep:
    i think i see it now, thanks for your help. i had to manipulate your method slightly though.
    Offline

    1
    ReputationRep:
    (Original post by marcusmerehay)
    i think i see it now, thanks for your help. i had to manipulate your method slightly though.
    Great. Let us know how you get on will you? I'm interested. It was about time I learnt about carbon dating. (Should be able to do a maths question without that knowledge of course).

    By the way can that negative value for dN/dt be correct?
    • Thread Starter
    Offline

    3
    ReputationRep:
    i think that's more to do with the fact that it is decay.
    Offline

    0
    ReputationRep:
    (Original post by rnd)
    Great. Let us know how you get on will you? I'm interested. It was about time I learnt about carbon dating. (Should be able to do a maths question without that knowledge of course).

    By the way can that negative value for dN/dt be correct?
    You usually put a negative infront to avoid a negative value.
    Offline

    1
    ReputationRep:
    The number of radioactive Carbon-14 atoms decaying was measured to be dN/dt = -6.08 per minute per gramme

    In living wood the decay rate is 6.68 particles per minute per gramme.
    Thanks. I was just puzzled that in the quote above one is negative and the other is positive.

    btw how did you get all that negative rep? I've noticed a few of your posts and they seem ok to me. I guess you got it in other forums.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Brussels sprouts
    Useful resources

    Make your revision easier

    Maths

    Maths Forum posting guidelines

    Not sure where to post? Read the updated guidelines here

    Equations

    How to use LaTex

    Writing equations the easy way

    Student revising

    Study habits of A* students

    Top tips from students who have already aced their exams

    Study Planner

    Create your own Study Planner

    Never miss a deadline again

    Polling station sign

    Thinking about a maths degree?

    Chat with other maths applicants

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.