Suppose a star rises due east, passes directly overhead, and then sets 12 hours after it rose. What is its average angular speed (in arcseconds per second)?
A)7.5
B)15
C)30
D)180

Question

Quizplus · Accepted Answer

The star completes a 180-degree arc in 12 hours. Since 1 degree equals 3600 arcseconds, the total arc is 180 * 3600 = 648,000 arcseconds. In 12 hours (or 43,200 seconds), the average angular speed is 648,000 arcseconds / 43,200 seconds = 15 arcseconds per second.

Suppose a Star Rises Due East, Passes Directly Overhead, and Then