Elevated Bridge B/C

[sewforlife]

At competition do judges mostly use rulers or blocks of solid material?
In my states, the judge used a clear glass cut-out square, and it had a pole in the middle, so he could stick it through the opening.

[andrewwski]

that's what i was basicly saying in the last part of my last post.

In the Wright Stuff rules it says that the motors have to 1.5 grams or less. Now the scales at the competition i procotred were purchesed by the Event supervisor ($200 each) and it was accurate to .01g. so what do we do with if the motors were 1.51, 1.52, 1.53, or 1.54? In my opinion i would allow them. the rules are only accurate to 0.1g. Also my MS doesn't even even have a scale to that accuracy and it was a regional competition so if schools can't affor expensive equipment they should be penalized for that. But really a .01 scale can be found for $12 online and mr. anderson recomends making your own. At the competition i proctored this case only came up with one motor and the ES said that it should be cut down to 1.50. I also agree that a clarification would be good.

I would agree with the ES. When someone says 1.5, you're supposed to assume that it equals 1.50000... and on and on.
.

No! You are not! That is incorrect scientific practice.

Being in Division B, you probably haven't learned about significant figures. You cannot make numbers more precise than they are. 1.5 means anywhere from 1.45 to 1.54. Therefore, in the context of this situation, 15.0 grams means anything from 14.95 grams to 15.04 grams. And last I checked, 15.004<15.04.

You NEVER assume a measurement is more precise than given. And a calculated number can never be more precise than any one of its components.

[sean9keenan]

I agree with Andrewwski, if they meant to have infinite sig figs they would have said 15 g, not 15.0 g, and being a scientific competition (one where sig figs play major roles in other events), it would seem that it should be measured to 15.0 grams (14.95 - 15.04 g) if that is what it says. Just like you would lose points on a Physics Lab test, why wouldn't you be able to "exploit" the rules in such a way where you could build to 15.04 grams if you wished?

Although that being said, on competition day the event supervisor can do what he will, the best you can do is be courteous, and get your coach if need be, trying to be reasonable and work something out.

And yes, I think that SO should publish guidelines for Sig-figs, in general they make me angry.

You don't like me when I'm angry

[croman74]

That's a good point. I didn't even know of this sig fig stuff. Then I completely agree with you guys. SO needs to be more specific. However, I think that most Event Supervisors will interpret it as 15 cm exactly.

[computernerd4826]

the only reason i know about sig. figures was from metric mastery
i just played it safe and made my bridge around 14.5

[croman74]

I didn't realize that you did bridge!
But I agree with computernerd; just play it safe and everything will be fine.

[computernerd4826]

yeah, i do a lot of building events
ill put them on my signature so nobody gets confused

[andrewwski]

14.5 is playing it very safe...half a centimeter could probably make a difference considering it's 6.67% of the total height of the main truss area.

I built mine to about 14.9, measured it in every area. When it was measured at regionals it measured in at exactly 15.0, which they did allow, but after I asked them to put it on the test base and measure it again, it was 14.9. Turns out the desk they were measuring them on at first must not have been perfectly flat.

[smartkid222]

If i could enlarge the clearence the clearence block in both dimentions it would have to be over 35.5cm x 9cm for my bridge not to clear, and my bridge height was 14cm. and i left a 1cm clear in the 5 cm on each side of the 45 cm clear span. (Div C)

I played it very, very safe.
I"m not saying to make it THAT safe, but you know i've had bad luck over the years.....

[croman74]

I wouldn't go .5 cm off, but I like a considerable amount of room.