Hi.
I have been lazy about my coverage of uncertainty this year. I have some catching up to do, and I am wondering if folks here can help me catch up in some way and improve how we do uncertainty in other ways.
What I normally do:
.have every kid measure the mass of the same thing, I enter it into a spreadsheet.
.we find the average, max & min
.throw out any unresasonable values.
We say the difference between the average and the max / min values is our uncertainty for measuring mass w/ a triple beam balance.
We do the same thing with a meterstick for measuring length, graduated cylinders and so on.
Then when we find a momentum value in a lab, we will find the value directly, then the largest and smallest possible values using the ranges we get from our devices listed above.
I believe many call this the 3 crank method.
Question 1:
If students want to determine the position of a moving object at a certain time, how do we determine the uncertainty in that measurement? How reasonable is it for a high school kid to say, "I measured 40.5cm +/- 3cm" based solely on their own confidence in the measurement? Is there a better way to determine this uncertainty?
Question 2:
I know uncertainty can also be done in quadrature, and through the use of partial derivatives. I never learned how these are known to be valid, or how they can be justified. If anyone has a link that demonstrates this, I would appreciate some help.
Question 3:
Do folks have a preference btn 3 crank, quadrature, and partial derivatives?