October 2009 SAT II - Physics

<p>I though resistance was 24 or sumthibg</p>

<p>not sure if i calculated it correctly</p>

<p>V=IR
120 = IR</p>

<p>P = I^2R
P = V/I
60 = 120/I
I = 2</p>

<p>V = Ir
120 = 2(R)</p>

<p>R=60</p>

<p>Oh and for the vertical circle with the string, was acceleration directed downwards at P?</p>

<p>Oh i used p = v^2/r</p>

<p>Binary Star System:</p>

<p>I have a tingling sensation its the angular momentum that is conserved since no external forces act of the system</p>

<p>Resistance is 240 ohms</p>

<p>We got bulb as being 60 W and 120 V soooo,</p>

<p>P=IV
60=120I<br>
I=.5</p>

<p>Now use V=IR</p>

<p>V/I=R</p>

<p>120/.5=240 ohms</p>

<p>And for the binary star Q, i said that the forces were constant.</p>

<p>I dont even remember the choices lol</p>

<p>Acceleration at P, anyone?</p>

<p>Spectravoid, tension is greatest at bottom of circle b/c it is rotating VERTICALLY</p>

<p>oh wow i’m an idiot</p>

<p>I replaced I^2R with V/I</p>

<p>lol i failed</p>

<p>Oh yes it was 240, i forgot to type the zero haha</p>

<p>Tension doesnt change. Its just that centripetal force changes cuz of mg</p>

<p>Resistance is 240 ohms</p>

<p>We got bulb as being 60 W and 120 V soooo,</p>

<p>P=IV
60=120I
I=.5</p>

<p>Now use V=IR</p>

<p>V/I=R</p>

<p>120/.5=240 ohms</p>

<p>WORD</p>

<p>@esplin. u r correct. max tension is at the bottom</p>

<p>What was the momentum of object X</p>

<p>I think the total Energy in the system was 144 J</p>

<p>How far did the little girl run b4 catching the ball? 5m?</p>

<p>I got 3m :/</p>

<p>I think the total Energy in the system was 144 J
agreed</p>

<p>yeah it was 1.5*2</p>

<p>What was the momentum of X</p>

<p>i said that 144 - 16 = Energy of x</p>

<p>so 128 = KE X</p>

<p>mv^2 = 256</p>

<p>i wasn’t sure what to do at that point</p>

<p>i picked the 2nd to last choice (16??)</p>

<p>@spectravoid i think it was 16</p>

<p>Oceanangel, thats only if it is rotating horizontally. You can even try this out.</p>

<p>Try rotating something vertically, the tension on the string is greatest on botom b/c it has MG acting on it. On the top, MG is cancelled out.</p>

<p>Omg i changed my answer to the wrong answer for the tension one… I always hoguht centripetal is sum of tension and mg</p>