the moon takes 27.3 days (2.36x10^6s) to orbit the earth . Calculate its distance from the earth . Take the mass of the earth to be 5.975x10^24kg.
Use the set formula T2=(4Pi^2/GM)R^3 and rearrange for r^3 to give
r3= T2GM/ 4Pi2
then insert values : r3 = (2.36x106)2 x 6.67x10-11x 5.975x1024/ 4PI2 = 5.62....x1025
Then take the cube root of R3 to give 3.830....x108. Question is in 3 sig fig so also give answer in 3 sig fig- so r= 3.83x108m (to 3 s.f) - which is the distance between the centre of the Earth and the centre of the Moon.
