The Official AP Physics B Thread

Test Preparation AP Test Preparation
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<ol>
<li>Two parallel wires, each carrying a current I, repel each other with a force F. If both currents are
doubled, the force of repulsion is
a. 2F b. 2 2 F c. 4F d. 4 2 F e. 8F</li>
</ol>

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<p>

</p>

<p>C? (10 characters)</p>

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<p>…is it c??</p>

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<p>its is c but why</p>

<p>also on the test when they dont specify charges is it usually a positive charge?</p>

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<p>Yes. Always assume that it is positive.</p>

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<p>F=ILB the B from a current carrying wire =UI/2piR, where U is a constant, I is current
F=ILUI/2piR</p>

<p>so if both currents are doubled, force is doubled (the 2 on the bottom cancels with the 4 on top, leaving 2)
A is the answer.</p>

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<p>4F? (10 char)</p>

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<p>could you make your answer choices clearer?</p>

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<p>ok I always forget why the work done in rotational acceleration is always zero, can someone explain this?</p>

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<p>to jarsilver:
because in rotational motion, the tension from the rope is perpendicular to the direction of motion</p>

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<p>can sum1 explain abut U = 3/2 nRT?</p>

<p>like when its used (possibly give an ex?)</p>

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<p>The distance traveled is 0. Thus, W = Fd=0 J</p>

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<p>So who else is completely screwed! whooo idiots!</p>

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<p>

</p>

<p>You’re not an idiot. The exam is just ****ing hard.</p>

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<p>im screwed… I get like half wrong on MC and half wrong on FRQ</p>

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<p>Yeah, if you don’t get a 5 on the Physics B exam…you’re far from an idiot. The test is hard, mostly because its scope is so damn wide. Hell, I’ve heard CB is considering moving some of its stuff to C because its so encompassing right now.</p>

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<p>oh I get it, W = Fd cos(theta) where the angle is 90 because the force is perpendicular, cos(90) is 0 so W is 0. thanks</p>

<p>yeah there is way too much on this test. it’s ridiculous that B has thermo and fluids questions when C doesn’t</p>

<p>I got a 25/70 on a practice multiple choice and a 46/80 on the free response :frowning: although I think that might actually work out to a 3.</p>

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<p>I got 20/66 in class when I took a practice test. lol I’m going to fail.</p>

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<p>here’s a sample scoring worksheet for anyone who wants it <a href=“http://02b9104.netsolhost.com/hiviz_org/apb89/ap/ap_exams/2004_AP_Scoring.pdf[/url]”>http://02b9104.netsolhost.com/hiviz_org/apb89/ap/ap_exams/2004_AP_Scoring.pdf&lt;/a&gt;&lt;/p&gt;

<p>I might actually be able to get a 4!</p>

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<p>65 (66 C, 4 W)/70 on MC, 77/80 on FRQ on the last one I took, but considering that I have Bio in the morning and Physics C afterwards, I doubt I’ll even be able to pull off a 70 combined =(</p>