Homework Help: "best" value for volume of a box

1. Sep 23, 2014

PhysicsMan999

1. The problem statement, all variables and given/known data
I'm given length, width and height of the box, all have uncertainties.

2. Relevant equations
V=lwh

3. The attempt at a solution
I've tried V=lwh, wasn't correct. Then V=lwh x (1 + relative uncertainty), wasn't correct. I just have no idea what the "best" value of a box is, my lab manual doesn't say anything about it, and I can't find anything on google either and I'm running out of tries. Appreciate any help!

2. Sep 23, 2014

Simon Bridge

You need to define "best value" for this problem - what does that mean?

Please provide the complete problem statement.
If you have $l\pm\sigma_l$, $w\pm\sigma_w$ and $h\pm\sigma_h$ as independent measurements of the dimensions of a rectangular box, then the volume of the box is $V=lwh\pm\sigma_V$.

So if that is not correct (how do you know?) then there is some information missing from the problem statement, or the solution attempt. i.e. how did you evaluate $\sigma_V$?

3. Sep 23, 2014

PhysicsMan999

That's the thing..I don't know what the "best" value is, and nowhere I've looked has told me what it means. And it's for an online assignment which I have 10 tries for, so it tells me whether the answer is right or wrong.

EDIT: Never mind. I can't believe how stupid the mistake I was making was..I just wasn't paying attention to the units. Measurements were given in cm, question wanted m^3. Sorry for wasting your time.

4. Sep 23, 2014

Simon Bridge

No worries - sometimes talking to someone else is what it takes to see the obvious right under your nose :)

BTW: whenever you have an answer you know is wrong - you should say how you know.
The assessment of the problem changes whether you got an answer different from a model answer, and answer that a human marked wrong, and an answer that a computer marked wrong.

You should also always show you working and reasoning ... seeing correct calculations and a "the computer rejected the result" would have got you specific and helpful advise right away.

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