- #1

OUmecheng

- 18

- 0

Mdot= mass flow rate

Ok so I found the change in mass by using the flow-rate and given time: m = (Mdot)(change in time) so m = (0.2kg/s)(10s) = 2kg

Then i found the uncertainty in the time and mass:

Ut = 0.2s/10s = 0.02s

Um= 0.05kg/2kg

Then I took uncertainty of the mass flow rate, which came from a bunch of partials like this (d is delta):

UMdot = +/- {[(m/Mdot)(dMdot/delta m)(Um)^2 + (t/Mdot)(dMdot/dt)(Ut)^2]}^(1/2)

Then

UMdot = +/- {[((1)( +/- 0.025)^2 + ((-1)(0.02)^2]}^1/2

=0.032 = 3.2%

BUT the answer is exactly half of that, 1.6%

Where the hell did I go wrong?

I can figure out b.) no problem once I figure out why the initial problem isn't working.