<p>OH ya bernoullis I got ya.
I was thinking of gases not fluids.</p>
<p>
</p>
<p>That doesn’t satsify:</p>
<p>A1v1=A2v2</p>
<p>
</p>
<p>That can’t be correct. The equation of continuity (A1V1 = A2V2) makes it clear that the opposite is true. Besides, if you look at the answers, they corroborate that velocity increases as area decreases.</p>
<p>The disk shaped head of a pin is 1.0 mm in diameter. Which of the following is the best estimate of the number of atoms in the layer of atoms on the top surface of the pinhead?</p>
<p>
</p>
<p>I just consulted the “Bible” myself. On page 143, it states:</p>
<p>“Because the produce Av is a constant, the flow speed will increase where the pipe narrows, and decrease where the pipe widens. In fact, we can say that the flow speed is inversely proportional to the cross-sectional area–or the square of the radius–of the pipe.”</p>
<p>OHHH OOOPSS!! typo!! scratch that thanks for catching me
geez how did i get that mixed up…</p>
<p>“speed increases as the area of the pipe decreases”</p>
<p>i’m dyslexic today
don’t be all up on my grillzzz sheesh</p>
<p>
</p>
<p>First, find the area of the head of a pin.</p>
<p>A = πr^2 = π(.001^2) = 3.14e-6 m^2</p>
<p>Now, find the area of an atom.</p>
<p>A = πr^2 = π((1e-10)^2) = 3.14e-20 m^2</p>
<p>Divide:</p>
<p>3.14e-6/3.14e-20 = 1e14 atoms</p>
<p>^^^ that will NEVER be on the ap test
guaranteed</p>
<p>are we suppose 2 know the radius of an atom? I didn’t know that. ty</p>
<p>^Haha, I’m LMAO, it WAS on the AP exam!! =) LOL</p>
<p>lol phew, thank god</p>
<p>^no don’t even worry about memorizing ANY constants
because for the mc, you can’t even use a calculator, so the toughest calculation you’d have to do would be like 4 (.001)= blah, and if there was a constant, just the symbol, (K, G, etc) would be in the answer choices</p>
<p>and a frq would not look like that because frqs rarely make you multiply out constants either…it’s all working with variables</p>
<p>oh and btw the “sample multiple choice questions” that are on cb for every ap tests are WAY harder than the actual ones</p>
<p>for the ap tests i’ve taken, i’ve looked at and done those sample questions, and for example for calculus, i got alot of those wrong, but on the real test, i wouldn’t be surprised if i got 100% of the mc correct(really easy for me)</p>
<p>those questions were never previously administered either, so don’t rely on them too much</p>
<p>and sure…that atoms on a pin questions could have been on an ap test…like and outdated ap test from a quarter of a century ago…like 1985, 1990</p>
<p>Dude Pigs…I have taken a released exam for the AP Physics B that had that exact question on it. You need to know some constants for the test…</p>
<p>
</p>
<p>Do not listen to this guy–he’s totally wrong. He is telling you that you don’t need to know that gravity is 9.8 m/s/s or that Avogadro’s number is 6.02e23.</p>
<p>If you’ve looked at any past AP exams, I can assure you both of these show up in the MC section. Now, you’re not expected to work with 9.8 or 6.02 because that would be a pain. However, the College Board does think that students are smart enough to work with 10 and 6.</p>
<p>You don’t have to use the precise constants, but you do need to rough them off. That means you need to know what the constants are.</p>
<p>^ i’m a girl btw</p>
<p>well DUH you need to know that g=10m/s^2 <em>rolls eyes</em>
but there are some stuff like mass of electron, mass of proton, mass of earth, radius of earth 1/4piE thingy, stuff like that that you don’t need to memorize!!</p>
<p>there aren’t like any released ap physics b tests from recent years, so all those practice tests are kinda outdated. sorry. 1998 is outdated. think about how many years have passed and how things have changed. that’s 21 years. 21 years in the world of science and testing</p>
<p>
</p>
<p>This discredits everything you’ve said. Since when is 1998 + 21 = 2009?</p>
<p>ok i meant 11 years geez
still outdated!!!
the calculus sample test from 98 was outdated!!!</p>
<p>you wanna memorize all of those friggin constants, then go ahead!!! geez just giving some advice</p>
<p>pigs, you do need to memorize constants…</p>
<p>You dont need constants!</p>