Question

in video lecture http://ocw.mit.edu/courses/physics/8-01sc-physics-i-classical-mechanics-fall-2010/introduction-to-mechanics/units-and-dimensional-analysis/ @29:10 prof.Lewine writes down the margin of error +/- 0,002. Where does he come up with that number? And @32:50 he writes down another margin of error, but now it is +/- 0,008. Where does this number come from?

Answer 1

He is estimating in the first case saying this is about how much he is uncertain in his measurement. From there anything he does mathematically to his equation he does to the margin of error. So all the intial margins of error are a measure of how much HE is UNCERTAIN.

Answer 2

Thank you, but I understand that already. What I don't understand@29:10 is exactly how he gets those two numbers MATHEMATICALLY. if h1/h2= ... +/- 0,06 how can in be that sqrt(h1/h2)=... +/- 0,002 ?
and @32:50 he says that 'by adding 0,002 and subtracting 0,002 there' he gets the uncertainty of 0,008. Can someone explain the math? Because how I see it the uncertainty should be 0,004...

Answer 3

because he had a number with uncertainty of 0.002 on one number and 0.006 on another and he summed them so 0.002+0.006=0.008