Join TSR now and get all your revision questions answeredSign up now
    • Thread Starter
    Offline

    0
    ReputationRep:
    Ok, so basically, I'm doing my mock analysis section later in the week, and we've been told that we need to do error bars for either the stress or strain (Young Modulus experiment), but not both, and that we need to choose the one that generates the most error.
    So, if i used a metre stick to measure length and extension, and a micrometer screw gauge to measure diameter, and a top-pan balance to measure the mass of the load, which would be likely to generate the largest percentage uncertainty, stress or strain?
    Or should I just work it out when I get to the lesson on Friday? And see which causes the greatest uncertainty by using maximum force and minimum area, and then the converse to find the uncertainty in stress, and then the maximum extension and minimum length, and then the converse to find the uncertainty in strain, and then compare the percentages? Does this method make sense?

    Thanks in advance
    • Study Helper
    Offline

    21
    ReputationRep:
    In all your calculations you take all readings (all have errors) and then substitute them into your formula.

    To find the max limit all multipliction terms must be maximised and all division terms must be minimised. This gives you your upper error.

    Do the reverse for the minimum error.

    The key is you need to find out the errors possible for each type of measuring instrument.
    Offline

    9
    (Original post by TeslaCoil)
    Ok, so basically, I'm doing my mock analysis section later in the week, and we've been told that we need to do error bars for either the stress or strain (Young Modulus experiment), but not both, and that we need to choose the one that generates the most error.
    So, if i used a metre stick to measure length and extension, and a micrometer screw gauge to measure diameter, and a top-pan balance to measure the mass of the load, which would be likely to generate the largest percentage uncertainty, stress or strain?
    Or should I just work it out when I get to the lesson on Friday? And see which causes the greatest uncertainty by using maximum force and minimum area, and then the converse to find the uncertainty in stress, and then the maximum extension and minimum length, and then the converse to find the uncertainty in strain, and then compare the percentages? Does this method make sense?

    Thanks in advance
    This is for a metal wire, I assume.
    You need to have an awareness of where the greatest %age uncertainty lies in individual measurements.

    Think:
    What sort of value do you expect for the extension of the wire?
    If you are measuring this extension with a metre rule, what is the % uncertainty in that? (A meter rule has a scale marked in mm.)
    You should find it to be rather large. Certainly larger than the other uncertainties.
    I suggest you measure the extension with some sort of vernier scale.
 
 
 
Poll
Which web browser do you use?

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.