- #1

lovelylm1980

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I can't figure it out it seemed so easy at first but then i got the wrong answer.

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- Thread starter lovelylm1980
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- #1

lovelylm1980

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I can't figure it out it seemed so easy at first but then i got the wrong answer.

- #2

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- #3

lovelylm1980

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- #4

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You got half the number expected?

Too late at night, I meant you got a surface tension "twice" what was expected.

Too late at night, I meant you got a surface tension "twice" what was expected.

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- #5

lovelylm1980

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do you mean that i should take my answer and divide by two or multiply by two?

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Post your answer --- we'll go from there.

- #7

lovelylm1980

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2.07 cm= .0207m

L= .0207m x 2= .0414m

1.90×10-2 N/ .0414m= .458 N/m

where do I go from here?

- #8

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1) remember the formula for circumference of a circle? 2πr

2) when you're pulling the loop from the surface of the liquid, you noticed that the surface "draped" BOTH directions from the wire? Does it make sense to you that you're actually pulling against surface tension exerted against twice the circumference of the wire loop? Once around for the outside of the loop, and once more for the inside?

3) What I come up with on the back of the envelope, and I'm truncating --- you'll have to take it beyond the single significant digit, is 0.07 N/m.

I thought at first that you were hung up on just the trick of doubling the circumference of the loop for this type of measurement --- that's why I said "half" mistakenly, and corrected things to guess that you were getting "twice" the value you were expecting, but it's more like 6 times larger than what your answer key is looking for.

This work for you?

- #9

lovelylm1980

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Thanks alot! You really helped me Igot the answer of 0.0731 N/m, and it was right thanks again.

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