<p>OK, last question, for the last minute studiers (Rupac got last one right).</p>
<p>A satellite of mass m is in a circular orbit around a planet of mass M. The time it takes to orbit once is:</p>
<p>A) proportional to sqrt(r)
B) inversely proportional to sqrt(r^3)
C) inversely proportional to sqrt(M) and proportional to r
D) proportional to sqrt(r^3) and inversely proportional to sqrt(M)
E) proportional to r and inversely proportional to sqrt(m)</p>
<p>Good luck on your test!</p>
<p>Hmm, Kepler’s Third Law:</p>
<p>T^2 = (4pi^2R^3)/(GM).</p>
<p>So, T is directly proportional to sqrt(R^3) and inversely proportional to sqrt(M).</p>
<p>(D).</p>
<p>will we actually need to know keplers laws?</p>
<p>2(pi)(R) is a length and T is time, so that expression is for speed. The first expression (GMm/R^2) is force.</p>
<p>so… done.</p>
<p>how was it guys? I found it pretty easy, a bit of time difficulty near the end due to overconfidence</p>
<p>REALLY didn’t like the mag. field types questions… didn’t cover that in school whatsoever…</p>
<p>yeah, me neither, but I studied up on it a bit and it helped quite a bit.</p>