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# Physics uncertainty problem watch

1. Using a micrometer screw gauge, I get 3 values for the diameter,d, of a wire each with +/- 0.01mm.
What's the uncertainty for the average value for d?

Then I have to use this average value in (πd^2)/4=A. What's the % uncertainty of A?
2. 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.

You can also find the Exam Thread list for A-levels here and GCSE here.

Just quoting in Puddles the Monkey so she can move the thread if needed
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(Original post by Puddles the Monkey)
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3. When you've taken repeat readings, the correct way to determine the percentage uncertainty is:

( (half the range) / (average value) ) * 100

That would give you the percentage uncertainty in d. You then double this to get the uncertainty in A (due to the d being squared).

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