Propagation of error - IB Physics
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- čas přidán 4. 07. 2024
- 00:00 Intro
0:21 Addition & Subtraction (concept / derivation)
3:15 Addition & Subtraction rule
6:03 Multiplication & Division rule
9:45 Rounding values with uncertainty
14:51 Other cases / rules
Thank you so much. Got a Physics test in 2 days, have had anxiety all term and as a result haven't been able to focus in classes. This video was a lifesaver!
How to derive these? By using calculus for subtraction,
f(x,y) = x - y
df(x,y) = dx - dy (but the rule says df(x,y) = dx + dy)
As well as in division,
f(x,y) = x/y
df(x,y) = dx/y - xdy/y^2
Dividing both sides by f(x,y) = x/y
df(x,y)/f(x,y) = dx/x - dy/y (but the rule says df(x,y)/f(x,y) = dx/x + dy/y).
Am I missing something?
thanks 4 the video dude its super helpful : )
Thank you so much for this video! I was lost until I watched it.
@Mr. Brown isn't the uncertainty supposed to be added as the percentage of the measured value for addition and subtraction? And then multiply by the calculated measured value to get the uncertainty?
Hi! That's the rule for multiplication / division - in addition/subtraction we simply add the absolute uncertainties together. The difference between absolute / percentage uncertainties and when to use which is the hardest part. Your data booklet does help if you learn how to decode it!
easy to comprehend............thanks
Well we get the simplicity of what we thought to be tough
Isn't this inaccurate? I don't know what "IB Physics" is (I'm foreign), but in my college experimental physics course I learned a different rule.
Consider an N-argument function F(x_1, ···, x_N), where ε(x_i) is the uncertainty of variable x_i.
What I learned is that ε(F) = √ ( Σ ( δF / δx_i )² · ε²(x_i) ).
For F(x, y) = x + y, this would yield ε(F) = √ ( y² · ε²(x) + x² · ε²(y) ), which is very different from the ε(x) + ε(y) formula that was presented in the video.
Hi Mr. Brown, I know this video is kind of old but I have an exam tomorrow and I don't seem to wrap my head around why in 12:15 we round it to 30 and not 33 ? or even 40 ? (40 because I thought errors should be rounded always upward ?)
It'd be amazing if you could resolve this doubt, thanks !
You need to round the the biggest value of the error (uncertainty), because we really don't need those other values when you are measuring an error. This is because we don't really know what happing in that big values and nether the less in those small values witch have extremely small impact.
Thank you!!
love it too, tx
love iiitt... 👍👍👍👍
Thank you
Nice 🤓🤓
It was really instructive. I shall be grateful to you if I have your opinion about my video in this topic.
completely different rules from this
for calc based physics fyi
yep! IB physics includes an intro to the basics of error propagation. You will use much deeper rules in college and beyond. The important thing is that we are communicating to each other how well we know what we know!
Suvk