Crave the Wave helpppppppp

[JustDroobles]

I have over 100% in Pre-Calculus and I've done Crave the Wave for two years at 9 different tournaments, including 1st place at Regionals two weeks ago. I've never known or been required to know Snell's law. In fact, I've never done math past basic algebra in Crave the Wave. I've never used used a trig function on a test. Knowing trig has been helpful for an understanding of the event, but I've never been tested on it.

[Phenylethylamine]

That's interesting. What state are you in? At both tournaments I've competed at so far this year (since I only picked up Crave this year)- Invitationals and the Eastern Long Island, NY Regionals- there were questions that required Snell's Law. There was a bonus question on the Invitational test that required serious trig, but none of the real questions involved anything more complicated than pressing the sine button (for the Snell's Law question).

[wlsguy]

The Northmont Invitational test has been added to the test exchange (thanks DarkSabre). It requires Snell's law.
Might be good practice for some teams. Good luck.

[EASTstroudsburg13]

I have over 100% in Pre-Calculus and I've done Crave the Wave for two years at 9 different tournaments, including 1st place at Regionals two weeks ago. I've never known or been required to know Snell's law. In fact, I've never done math past basic algebra in Crave the Wave. I've never used used a trig function on a test. Knowing trig has been helpful for an understanding of the event, but I've never been tested on it.

Basic algebra like what? Just the regular formulas?

[JustDroobles]

That's interesting. What state are you in? At both tournaments I've competed at so far this year (since I only picked up Crave this year)- Invitationals and the Eastern Long Island, NY Regionals- there were questions that required Snell's Law. There was a bonus question on the Invitational test that required serious trig, but none of the real questions involved anything more complicated than pressing the sine button (for the Snell's Law question).

I'm in Region 12, in Michigan. Our Regionals, this year and last year, have had a bunch of different stations set up with demonstrations and experiments where we had to describe and interpret wave phenomena. (I know this sounds easy, but I kind of oversimplified it) I got 2nd last year and 1st this year. Please don't bash me for saying this, because I'm just saying what I've been told, but I've been told that Region 12 is the hardest in the nation. We have over 40 teams, including consistently National teams and the GVSU professors write crazy-difficult tests.

Now that I've read up on Snell's law, it does seem very useful. I can't remember any specific occasion, but I may have had an opportunity to use it that I just didn't realize.

[Phenylethylamine]

We also have well over 40 teams in our region- I think most of the NY regions do- but yours could well be more difficult than ours, since we're the only consistent National team in B Div in our region.

Snell's Law is incredibly useful. Do you know of any other method of doing the same sort of problem?

[rbejnood]

snell's law is pretty basic and easy trig. there is a diagram on wikipedia that explains a lot if you are looking at the formulas to the right of it.

[JustDroobles]

Snell's Law is incredibly useful. Do you know of any other method of doing the same sort of problem?

No; I think any other time I've been asked a problem related to Snell's law it has been multiple choice and I've figured it out by logic, not math. I did that Northmont invitational test now - it was good practice. And Snell's law IS incredibly useful.

Now that I think about it, I think there was a tie-breaker at our regional that could have been solved using Snell's Law. I know I didn't leave it blank, but I don't remember how I solved it. After doing an experiment with refraction in a square of glass, we were asked to calculate its index of refraction. (again, as a tie-breaker) I've never been tested on it in an invitational, but I have been asked in a few online tests.

[blue cobra]

On the Northmont test, #8 and #12 use a triangle symbol (no clue what it's called) to represent some sort of difference. Number 12 is about doppler, and the fomula (from the wiki) f'=f+fv/c doesn't seem to work. Could anyone be as neighborly as to explain these to me?

[chia]

On the Northmont test, #8 and #12 use a triangle symbol (no clue what it's called) to represent some sort of difference. Number 12 is about doppler, and the fomula (from the wiki) f'=f+fv/c doesn't seem to work. Could anyone be as neighborly as to explain these to me?

i'm pretty sure the triangle is called delta, it means "change in". we used them in geometry and in algebra for the slope formula (delta y over delta x = change in y over change in x)

[wlsguy]

On the Northmont test, #8 and #12 use a triangle symbol (no clue what it's called) to represent some sort of difference. Number 12 is about doppler, and the fomula (from the wiki) f'=f+fv/c doesn't seem to work. Could anyone be as neighborly as to explain these to me?

The triangle is the delta symbol. It refers the difference in time for question #8 (73 sec) and the difference in speed for # 12 (30m/s).

Question number 12 is shown a little differently than the wiki formula to help explain it.
The answer starts with the wavelength if the source was not moving. =1.14m This uses only the speed of sound.343 m/s
The next computation calculates the wavelength of the 30 m/s movement = .1m

To get the final answer you need to subtract the movement effect from the stationary amount to get the wavelength that you hear of 1.04m.
You then plug the 343m/s / 1.04m to get the answer = frequency of 329.81hz.

[blue cobra]

Thanks, I understand it a lot more now. And now that you mention it, I do remember the delta from the slope formula.