<p>how do you do the questions that, after providing you a chart, ask something like, "which of the following photon energies could NOT be found in the emission spectra of this atom after it has been excited to the n = whatever state? doesn’t it have to do with the difference in the energy levels or something?</p>
<p>can someone define work impulse power and momentum and how they all relate to each other</p>
<p>P(power) p(momentum) W(work)</p>
<p>P=W/s=Fv, p=mv=Ft, W=Fd</p>
<p>And impulse is the change in momentum, I think.</p>
<p>Hopefully those formulas are right.</p>
<p>thanks big help</p>
<p><a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
<p>Need explanations for #9, 12, 17, and 18 on the Sample Multiple Choice.</p>
<p>A certain crane can provide a maximum lifting force of 25 000 N. It hoists a 2000-kg load starting at ground level by applying the maximum force for a 2-second interval; then, it applies just sufficient force to keep the load moving upward at constant speed. Approximately how long does it take to raise the load from ground level to a height of 30 m?</p>
<ol>
<li><p>W= pressure times change in volume. If there’s no work done, then there’s no change in volume. Therefore, choose B.</p></li>
<li><p>C=Q/V.</p></li>
<li><p>Well, D looks strange, but I don’t know why it’s wrong. My teacher covered the entire optics and waves chapter in one class period.</p></li>
<li><p>Photon has less energy since electron gains energy and E=hf, so frequency of the photon must go down.</p></li>
</ol>
<p>By the way, is Doppler’s Effct on the exam?</p>
<p>sorry for reposting the question</p>
<p>i dont even remember posting that :S</p>
<p>can any1 explain #2 on that?</p>
<p>Need explanations for #11,12,13 on the Sample Multiple Choice plzz</p>
<p>How is everyone memorize the equations of the list? Flash cards? Repetition?</p>
<p>A block of mass 3.0 kg is hung from a spring, causing it to stretch 12 cm at equilibrium, as shown above. The 3.0 kg block is then replaced by a 4.0 kg block, and the new block is released from the position shown above, at which the spring is unstretched. How far will the 4.0 kg block fall before its direction is reversed?</p>
<p>
</p>
<p>This is a F = kx problem. First, we need to solve for the spring constant, k.</p>
<p>F = 30 N (which was derived by 3*10), x = .12 m, k = ?</p>
<p>30 = .12k</p>
<p>k = 30/.12 = 250</p>
<p>Now, we need to replace this 3 kg block with a 4 kg block and calculate x with F = kx.</p>
<p>So now we have F= 40 N, x = ?, k = 250</p>
<p>40 = 250x</p>
<p>x = 40/250 = .16 m</p>
<p>It is .16 m above equilibrium before being dropped, so when it is dropped, it will go .16 m below equilibrium. Therefore, we have:</p>
<p>total distance = .16 + .16 = .32</p>
<p>Hope that helps.</p>
<p>kd=mg
*find k first
k=(3)(10)/(.12)= 250 <–spring constant</p>
<p>kd=mg again
250d=4(10)</p>
<p>d=.16 meters= 16 centimeters</p>
<p>is that right??
thanks for the problem</p>
<p>
</p>
<p>No, that’s incorrect. You calculated d correctly, but you need to multiply it by 2 because it is 16 cm ** above ** equilibrium.</p>
<p>yeah can someone w/ good command of circuits please explain numbers 11 and 12 on the collegeboard’s practice multiple choice in the course description? also number 7 and 13 please.</p>
<p>
</p>
<p>Answers: B, B, B.</p>
<p>** Explanation for #11 **</p>
<p>Since the switch is open, the whole circuit is in series–no current flows to the branch with a capacitor. Therefore, you add up the resistors (10 + 6 + 4 = 20 Ω), and you plug it in to the equation V = IR, where V is given as 12 V. You have:</p>
<p>12 = 20I</p>
<p>I = 12/20 = 3/5 = .6 A</p>
<p>** Explanation for #12 **</p>
<p>Now the switch is closed, and the capacitor is fully charged. What’s important to know here is that when the capacitor is fully charged and shuts down a branch of a circuit, it’s voltage is equal to the voltage that would otherwise be going through that branch. Since there are 12 V total, and there is a parallel split, the voltage splits in half to 6 V per branch, too. Therefore, the voltage across the capacitor is 6 V.</p>
<p>** Explanation for #13 **</p>
<p>To determine the velocity, we use A1V1 = A2V2. Since the area of 1 is larger than the area of 2, the velocity of 1 must be less than the velocity of 2.</p>
<p>To determine the pressure, we see that there’s more space for more fluid in area 1, so the pressure is greater there. (If anyone has a better reason, please do post it.)</p>
<p>wait, how do u know it is 16 cm above equilibrium. ?</p>
<p>"To determine the pressure, we see that there’s more space for more fluid in area 1, so the pressure is greater there. "</p>
<p>Pressure is force/area…so wouldn’t it be the opposite?</p>
<p>
</p>
<p>I have no idea on that one. Someone else please post how to solve it! (The velocity part is right, though.)</p>