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    hi, this is a BMAT question and its really hard!

    A length of plastic tubing weighs 1.2g. When filled with isotonic saline it weighs 18g. If the diameter and the length of the tubing are both doubled, what would be the total mass of the tubing and saline once completely filled? (NB the tubing is open at both ends.) Give your answer to the nearest gramme
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    Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

    Just quoting in Danny Dorito so she can move the thread if needed :wizard:
    (Original post by Danny Dorito)


    The weight of tubing will increase by 2 because of doubling length and by 2 because of doubling diameter (Circumference will increase by pi X 2d / pi X d = twice. Total INCREASE = 4X So mass of tubing = 1.2 X 4 = 4.8 g [ASSUMPTION: thickness of tubing remains constant)

    Weight of saline will increase proprtionally to increase in volume: pi X (2r)2 X 2l divided by pi X r2 X l = 4r2/r2 X 2l/l = 8X so mass of saline = 16.8 (differece between original total mass of 18g and ubing mass of 1.2g) X 8 = 134.4g

    TUBING + SALINE mass = 134.4 + 4.8 = 139g to nearest gram.

    Hope this helps!
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