The Solar System – ASTR 121

First Midterm – January 28, 2015, 9:00-9:50

Instructions:  Print your name and student identification number at the top of this page.  Answer each of the questions A through J in the space provided.  Be clear and thorough in your answers using sentences, labeled diagrams, and formulas with symbols defined, where appropriate.  Each question is worth two points.

A.  Explain what the ecliptic plane is.

B.  Explain why we don't see an eclipse at every new and full moon.

C.  Explain what an Equinox is.

D.  Explain why we can measure only the angular distances between objects in the sky.

E.  Define the foci and semi-major axis of an ellipse.

F.  State Kepler's third law of planetary motion.

G.  State Newton's law of universal gravitation.

H.  Why do we have two high tides and two low tides per day?

I.  Explain the difference between a bound and unbound orbit.

J.  Traveling at about 3x10⁵ km/s, how long would it take light to go the distance of about 4x10⁵ km  from the Earth to the Moon?