Chapter 12, Problem 24PCE

Predict/Explain The Earth-Moon Distance Is Increasing Laser reflectors left on the surface of the Moon by the Apollo astronauts show that the average distance from the Earth to the Moon is increasing at the rate of 3.8 cm per year. (a) As a result, will the length of the month increase, decrease, or remain the same? (b) Choose the best explanation from among the following:

1. I. The greater the radius of an orbit, the greater the period, which implies a longer month.
2. II. The length of the month will remain the same due to conservation of angular momentum.
3. III. The speed of the Moon is greater with increasing radius; therefore, the length of the month will decrease.