# physics

posted by
**Michelle**
.

The moon is receding from the Earth by approximately 3.8 cm per year. Earth's mass is 5.98 x 10^24 kg, and its radius is 6.38 x 10^6 m. The Moon's mass is 7.3 x 10^22 kg, its radius is 1.79 x 10^6 m, and its orbital period around Earth is 27.3 days. The current average distance between the 2 surfaces is 3.85 x 10^8 m. Assume that neither body gains or loses mass and that the recession continues at a rate of 3.8 cm per year.

a.) Approximately how much will the gravitational attraction between the Moon and Earth change between now and 499 million years from now?

b.) Approximately how long, in present Earth-days, will it take the Moon to orbit Earth 499 million years from now?