<p>^Yeah I realized that after I took the test. I was like -______-</p>
<p>As for the Jupiter question, gravitational potential energy is the greatest when the planet is at its farthest. Gravitational acceleration gets stronger when the planet is closer to the Sun due to F = GM1M2/R^2</p>
<p>Mononofu you’re aboslutely right
<p>@ bravosix I think gravitational potential energy decreases as the distance (radius) increases. its basically the same formula as force due to gravity except the radius isn’t squared. so the Jupiter problem is probably just that it’s fastest around the sun.</p>
<p>@jumpshooter Remember, gravitational potential energy is -GM1M2/R. Even though the absolute value would be less when the planet is further away, the figure is negative, so potential energy would increase as the planet is moving away from the Sun. I did the same thing you did, and only realized this after the test.</p>
<p><a href=“Gravitational energy - Wikipedia”>Gravitational energy - Wikipedia;
<p>does anyone know the answer to the electroscope questions?
i guessed move apart (electrons) and no apparent change (copper wire)</p>
<p>I got the same answers for the electroscope questions and it specified that the copper wire was grounded.</p>
<p>@joiklg: do u remember what the question was?</p>
<p>i think if the node or something like that was given a negative charge what would happen to the flaps
the other one was what change would you observe if a copper wire touched the node</p>
<p>Would they fall vertical upon the grounded copper wire’s contact?</p>
<p>Yeah, I believe so</p>
<p>For the ball hanging from a string, i put the tension = the weight of the ball - the force exerted by the ball on earth, since the force exerted by the ball on earth is so small that it can be regarded as 0, so the tension is equal to the weight of the ball. can anyone confirm the question? I may probably read the answer wrong.</p>
<p>that was such a weird question. i left it blank. It made no sense to me whatsoever.</p>
<p>@Guangzhun, crap, I thought they were all equal? cause F = Gm1m2/r^2 for both the force exerted by the ball on the Earth and for the force exerted by the Earth on the ball?</p>
<p>No, the ball exerts an equal force on the earth as the earth does on the ball. It’s the acceleration that’s almost zero, not the force. I put that all 4 forces are equal.</p>
<p>Someone mentioned substituting a chunk of GM/r in to find v, does anyone remember exactly what they subbed?
I put the square root of Fr/m or something</p>
<p>Was the one revolving around the wire same as going left ? o__o</p>
<p>Yeah, I got v = sqrt(Fr/m). I derived it from F = (mv^2)/r.</p>
<p>As for your second question, I’m not sure what you’re asking.</p>
<p>no problem… it was from 2 pages ago haha.
it’s the compass needle over a current problem, which direction does it turn?</p>
<p>Oh! It is to the left. Magnetic field lines go in circles around a wire carrying a current.</p>
<p>Hi! for the last question, what did you guys get. Doesn’t it ask for the parallel speed of the plane to the ground or something?</p>