Simple Machines B/Compound Machines C

sciolyboy123 · Post by **sciolyboy123** » Sat Apr 18, 2015 4:08 pm

Unome wrote: Yeah, the same thing happened to us on the test at Dodgen; we spent 10 minutes working out a problem (which now seems sort of easy) only to find out that the answer was 1.

I think i know which question that is.

Userpage · Post by **Unome** » Sat Apr 18, 2015 4:41 pm

sciolyboy123 wrote:
Unome wrote: Yeah, the same thing happened to us on the test at Dodgen; we spent 10 minutes working out a problem (which now seems sort of easy) only to find out that the answer was 1.
I think i know which question that is.

The double-fulcrum, right? All of the tests at Dodgen made me so much better at my events (although it was a hard transition from that difficulty level to Regionals)

RontgensWallaby wrote:Thanks so much, guys. I remember solving it twice and getting something around there the first time but thinking that was too shallow of an angle if that much of the input work was converted to friction.
Unome wrote: Yeah, the same thing happened to us on the test at Dodgen; we spent 10 minutes working out a problem (which now seems sort of easy) only to find out that the answer was 1.
Was it the final question?

No, that one was different (I figured it out after we got the results back). It was the double-fulcrum problem (like #47 or something)

Userpage · Post by **Unome** » Sat Apr 18, 2015 4:42 pm

EDIT: Forgot that I posted just 30 seconds ago on the same thread; page splits are annoying. Moved upward

RontgensWallaby · Post by **RontgensWallaby** » Sat Apr 18, 2015 4:44 pm

Yeah, I know... Regionals was SO much harder than Dodgen Inv...

Userpage · Post by **Unome** » Sat Apr 18, 2015 4:47 pm

RontgensWallaby wrote:Yeah, I know... Regionals was SO much harder than Dodgen Inv...

If this is sarcasm (which I'm not entirely sure about, although I really should be) you should try to denote it as such (Some people use <sarcasm>text</sarcasm>)

sciolyboy123 · Post by **sciolyboy123** » Sat Apr 18, 2015 5:01 pm

Actually my regionals was so much easier than Dodgen!!!!

Simple Machines was 10 multiple choice questions
Disease Detectives had the most basic thing ever (20 questions)

RontgensWallaby · Post by **RontgensWallaby** » Sat Apr 18, 2015 6:06 pm

Same, we had only 10 multiple choice questions. Re-checked like 4 times and got out within 10 minutes. Easy but disappointing...

Userpage · Post by **Unome** » Sat Apr 18, 2015 6:25 pm

RontgensWallaby wrote:Same, we had only 10 multiple choice questions. Re-checked like 4 times and got out within 10 minutes. Easy but disappointing...

Yeah (although it was better than last year's 7 questions)

sciolyboy123 · Post by **sciolyboy123** » Sat Apr 18, 2015 6:26 pm

Lol, it sounds to me that at regionals, everyone has 10 questions or less

Post by **UTF-8 U+6211 U+662F** » Sun Apr 19, 2015 9:06 am

Unome wrote:
Giant Mole Squad wrote:Does anyone know how to solve number 4 on the Captain's Tryouts test for Compound Machines?
Yeah, I spent so much time trying to figure out that one (and I still don't know); I never understood tension beyond what I needed to solve Div B level problems.

I think some free body diagrams would help here.

EDIT: I believe it's solved like this: $\Sigma F = ma \\* m_1 g - T = m_1 a \\* 2T - m_2 g = m_2 a \\* 2T = m_2 g + m_2 a \\* T = \frac{m_2 g + m_2 a}{2} \\* \frac{m_2 g - m_2 a}{2} - m_1 g = m_1 a \\* a = \frac{\frac{m_2 g - m_2 a}{2} - m_1 g}{m_1} \\* a = \frac{m_2 g - m_2 a - 2m_1 g}{2m_1}$
for first mass, and then just do the same thing for the other masses.
Hmm, the key says something different.

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Simple Machines B/Compound Machines C

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