2 Whenever two {\em Apollo} astronauts were on the surface of the Moon,
3 a third astronaut orbited the Moon. Assume the orbit to be circular
4 and $r_1=100\U{km}$ above the surface of the Moon. At this altitude,
5 the free-fall acceleration is $g=1.52\U{m/s}^2$. The radius of the
6 Moon is $r_0=1.70\E{6}\U{m}$. Determine
7 \Part{a} the astronaut's orbital speed $v$ and
8 \Part{b} the period of the orbit.
9 \end{problem*} % problem 5.18
13 Using the basic formula for circular motion
15 a_c &= \frac{v^2}{r} \\
18 =\sqrt{1.52\U{m/s}^2 \cdot (1.00\E{5} + 1.70\E{6})\U{m}}
23 The astronaut travels the circumference at a constant speed so
25 \Delta_x &= v \Delta_t \\
26 T &= \frac{2 \pi r}{v}
27 =\frac{2 \pi r}{\sqrt{a_c r}}
28 =2 \pi \sqrt{\frac{r}{a_c}}
29 =2 \pi \sqrt{\frac{(1.00\E{5} + 1.70\E{6})\U{m}}{1.52\U{m/s}^2}}