Question

1. the diagram below shows a model of the moons orbit around earth. letters a, b, c, and d represent four positions in the moons orbit.

what is the approximate length of time the moon takes to travel from position a to position d?
(1) 22.5 days (2) 29.7 days (3) 15 days (4) 7.5 days
base your answers to questions 19 and 20 on the diagram below and on your knowledge of earth science. the diagram represents the moon at different positions in its orbit around earth. the phases of the moon as seen by an observer in new york state have been labeled.

1. eclipses do not occur each time that the moon revolves around earth because the moons

(1) diameter is greater than earths diameter
(2) orbit is inclined to earths orbit
(3) diameter is less than earths diameter
(4) orbit is less eccentric than earths orbit

Explanation:

Question 18

The Moon's orbital period (sidereal period) is ~27.3 days, but the synodic period (time between phases) is ~29.5 days. However, the four positions A-D divide the orbit into 4 equal parts. Each quarter takes ~7.4 days (29.5/4 ≈7.4), closest to 7.5 days.

Eclipses require the Moon, Earth, and Sun to align perfectly. The Moon’s orbit is tilted ~5° relative to Earth’s orbital plane (ecliptic), so alignment only happens at nodes, not every orbit.

Answer:

(4) 7.5 days

Question 19