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# Uncertainties( Raising to a fractional power) Watch

1. I know that if value a is raised to the power n then the percentage uncertainty = n*(delta a/a)*100 but what if n = 1/k (k where is any number greater than 1). What do i do?
I know that if value a is raised to the power n then the percentage uncertainty = n*(delta a/a)*100 but what if n = 1/k (k where is any number greater than 1). What do i do?
It's still times n.
If you have a square root (power half) then the % uncertainty is halved.
3. (Original post by Stonebridge)
It's still times n.
If you have a square root (power half) then the % uncertainty is halved.
Does logs affect the value?
Does logs affect the value?
Yes.
If you have loge of a number N with an uncertainty ±n it's done as follows
x = loge (N ± n)
Gives Loge N ± n/N

So if you have a length measured as, say, 50m ± 2m
Then the uncertainty in the loge is just 2/50
Giving Loge(50) ± 2/50
Giving 3.91 ± 0.04

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Updated: April 14, 2013
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