May SAT II Physics Discussion

Test Preparation SAT Subject Test Preparation
181

<p>K I was looking everywhere for curve but all I could find was this 1, thanks</p>

182

<p>richyrich, i understand what u are saying but centripital acceleration is still acceleration… the only force in the diagram is the sun, thus the acceleration had to point that way, and the velocity which is instantaneous, is always tangential</p>

183

<p>we can’t really judge anything off of previous test for ourselves…</p>

<p>if any of you guys use books like kaplan / mcgrawhill you’ll notice they have one standardized score conversion for all their pratice exams (which are 10x easier than the actual exam)</p>

184

<p>this is pretty accurate [ <a href=“http://talk.collegeconfidential.com/4220732-post10.html[/url]”>http://talk.collegeconfidential.com/4220732-post10.html&lt;/a&gt; ]</p>

185

<p>@zkaplove17, true that velocity is instantaneous, but acceleration is the derivative of velocity, which is the change of velocity over time. In elliptical orbit, velocity is always changing, so there is always tangential acceleration. I am 100% certain the the acceleration is the vector of tangential and centripetal acceleration, and not just the centripetal component, because purely if it were straight down, the orbit would be perfectly circular.</p>

186

<p>id guess (same format as the previous link) that for this test it will be Physics - 75 - 57 - 42 - 28</p>

187

<p>Okay, acceleration is proportional to Force; since the only force comes from the sun, the acceleration vector points towards the sun.</p>

188

<p>

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<p>In order for the acceleration to NOT point at the sun, there has to be a force acting on the comet OTHER than the gravitational force of the sun. What is that force?</p>

189

<p>this wasn’t the exact question, but same concept
<a href=“http://www.batesville.k12.in.us/physics/phynet/mechanics/gravity/answers/images/ch14_rev7.gif[/url]”>http://www.batesville.k12.in.us/physics/phynet/mechanics/gravity/answers/images/ch14_rev7.gif&lt;/a&gt;&lt;/p&gt;

190

<p>im not saying the acceleration is down, its pointed toward the sun, keep in mind that F = Gm/r, acceleration exists because of a force, this question wasnt so analytical</p>

191

<p>Guys, where was the sun in the problem?</p>

192

<p>RichyRich…what are you actually arguing for? What do you think is the correct answer. V tangent A pointing southwest at the sun? because I think we established that earlier.</p>

<p>And if you are saying that the acceleration vector would point half way between the tangent and toward the sun, that is definitely wrong lol</p>

193

<p>@Andrew and Garfield, if you take Physics C you will learn that angular momentum must be conserved in any orbit, where L (angular momentum) = Iw(angular velocity). The tangential acceleration of nonuniform orbit is dw/dt=a(tangential)/R. Since the angular velocity is not constant in elliptical orbit due to Kepler’s Laws, there IS tangential acceleration. There is no “Force” that causes this, but simply the fact that momentum must be conserved. Newton’s 2nd law does not apply in this situation.</p>

194

<p>did u guys that the frequency increases when approaching decreases as it moves away?</p>

195

<p>I am in Physics C. And yes, there is tangential acceleration. If you looked at the problem (and the picture linked to above), you could see that the vector wasn’t perpendicular to the velocity. In other words, it could be split up into its tangential and centripetal components. The acceleration vector in the picture was the sum of these two components. You’re making this much more complicated than it needs to be–and you’re making mistakes in the process.</p>

<p>And acceleration is ALWAYS caused by forces. There’s no exception, except maybe when you get to the sub-atomic level or something.</p>

196

<p>The correct answer is that acceleration is pointing to the bottom left.</p>

197

<p>Yes, I did, zkaplove17.</p>

<p>Was the sun directly underneath or off to the side?
So is the answer directly down or pointing southwest?</p>

198

<p>haha richy rich thats wat all of us have, idk why u were arguing</p>

199

<p>it was down to the left, i hate this one post per minute thing</p>

200

<p>Actually AndrewT, the comet was directly over the the sun, and the acceleration vector that pointed to the sun was perpendicular to the velocity vector, so your assumption there is incorrect. In the diagram, the sun was actually in the center of the elliptical orbit. I remember clearly because I definitely worked out the concepts down for a good couple minutes on this problem.</p>