Simple Machines B/Compound Machines C

[chalker]

We figured that the event creators probably designed the event this way

Yes we did;)

[blindmewithscience]

This seemed better but it has a major flaw! I wont tell what it is though. Just throw some examples into the equations and remember: we have no way of knowing exactly how much the masses weigh and many will have trouble determining which mass is heaviest - especially when they are very close.

Ah, figured it out. Nice find Totally didn't see it before now. My team will probably just stick with the other design, then. It's just taking one problem and creating another, if I understand it right.

[hscmom]

So, now that we've got our (basic) lever made, help me understand the rules. The students are given masses A, B and C, but nowhere it says that A <= B <= C. So, you could have B being the heaviest, C the lightest, and A in the middle (or any other combination, including A = B = C). The answer is supposed to be A/B and B/C. And am I correct in that B = B in both of those. Let's just assume the masses are 600 grams, 550 grams, and 720 grams. Then, the students could give the ratios as 60/55 and 55/72, right? do they have to simplify 55/60 to 11/12? Do they have to make A = 1?

I just want to make sure I'm teaching them right how to report their findings AND make sure I am not introducing extra, time-consuming steps. I want them to get to the first acceptable answer and have the timer stop.

Thanks

[chinesesushi]

So, now that we've got our (basic) lever made, help me understand the rules. The students are given masses A, B and C, but nowhere it says that A <= B <= C. So, you could have B being the heaviest, C the lightest, and A in the middle (or any other combination, including A = B = C). The answer is supposed to be A/B and B/C. And am I correct in that B = B in both of those. Let's just assume the masses are 600 grams, 550 grams, and 720 grams. Then, the students could give the ratios as 60/55 and 55/72, right? do they have to simplify 55/60 to 11/12? Do they have to make A = 1?

I just want to make sure I'm teaching them right how to report their findings AND make sure I am not introducing extra, time-consuming steps. I want them to get to the first acceptable answer and have the timer stop.

Thanks

Unfortunately no one can answer this question except for maybe chalker. You should submit a rules clarification. B = B because each of the masses are labeled and the labels won't change when you're changing your answer, but for the format of the answers you should submit a rules clarification.

[Unome]

So, now that we've got our (basic) lever made, help me understand the rules. The students are given masses A, B and C, but nowhere it says that A <= B <= C. So, you could have B being the heaviest, C the lightest, and A in the middle (or any other combination, including A = B = C). The answer is supposed to be A/B and B/C. And am I correct in that B = B in both of those. Let's just assume the masses are 600 grams, 550 grams, and 720 grams. Then, the students could give the ratios as 60/55 and 55/72, right? do they have to simplify 55/60 to 11/12? Do they have to make A = 1?

I just want to make sure I'm teaching them right how to report their findings AND make sure I am not introducing extra, time-consuming steps. I want them to get to the first acceptable answer and have the timer stop.

Thanks

Unfortunately no one can answer this question except for maybe chalker. You should submit a rules clarification. B = B because each of the masses are labeled and the labels won't change when you're changing your answer, but for the format of the answers you should submit a rules clarification.

I don't really understand the middle parts, but for how to write the ratios I've just decided to ask the proctor at every competition I go to.

[chalker]

So, now that we've got our (basic) lever made, help me understand the rules. The students are given masses A, B and C, but nowhere it says that A <= B <= C. So, you could have B being the heaviest, C the lightest, and A in the middle (or any other combination, including A = B = C). The answer is supposed to be A/B and B/C. And am I correct in that B = B in both of those. Let's just assume the masses are 600 grams, 550 grams, and 720 grams. Then, the students could give the ratios as 60/55 and 55/72, right? do they have to simplify 55/60 to 11/12? Do they have to make A = 1?

First off, usual caveat about this not being the site for official comments or clarifications. Please visit soinc.org for that.

Regarding your various comments:
-Correct, nowhere is it stated A < B < C in mass. I'd suggest you be prepared for any of them to be the heaviest and any to be the lightest.
-B does equal B in both answers you have to give (A/B and B/C).
-Regarding the format of the answers, I'd suggest you ask each event supervisor since it's really up to their discretion. You might be able to write something like 55/72, or might be asked to give the decimal equivalent (.7638)

[retired1]

Would not the 0.7638 violate the significant digits?

[joeyjoejoe]

I just noticed that nowhere in the rules does it state where on the beams you are required to place the weights. What's to prevent someone from bringing their Class1/Class 2 combo to impound yet only utilizing the class one lever for the event? This would seem much easier to accomplish. Would this be a violation of the "spirit of the problem" mentioned in the general rules section?

[chinesesushi]

Would not the 0.7638 violate the significant digits?

I believe the significant digits rules only pertains to the written section, because that's the only place requirement is listed. Being as such, the way the scoring works it looks like it does not matter whether or not you include significant digits; however, I suggest submitting a rules clarification or asking the event supervisor at the competition what they desire about whether or not they want you to factor in significant figures in the answers for the ratio.

I just noticed that nowhere in the rules does it state where on the beams you are required to place the weights. What's to prevent someone from bringing their Class1/Class 2 combo to impound yet only utilizing the class one lever for the event? This would seem much easier to accomplish. Would this be a violation of the "spirit of the problem" mentioned in the general rules section?

Rule 5d. prohibits that. "...or those that do not make an honest attempt to utilize a compound lever to determine the mass ratios receive R1 & R2 & TS of 0.

[chalker]

Would not the 0.7638 violate the significant digits?

I believe the significant digits rules only pertains to the written section, because that's the only place requirement is listed. Being as such, the way the scoring works it looks like it does not matter whether or not you include significant digits; however, I suggest submitting a rules clarification or asking the event supervisor at the competition what they desire about whether or not they want you to factor in significant figures in the answers for the ratio.

Also note that in Part 2, your score is based upon how close you are to the correct answer. Thus even if you add in random extra digits, the event supervisor already has a good way to 'penalize' you for not getting the correct answer - there is no mechanism to completely dq your answer just because you didn't follow sig fig rules in your calculations.

The whole purpose of sig figs is to help ensure estimation errors don't end up propagating through scientific experiments and calculations such that they end up being viewed as important (e.g. to ensure not just accuracy, but also precision). That doesn't really apply to the device testing portion of this event, since we are just asking you to try to estimate the masses as quickly and best you can.