Physics question?

Question

The orbit of a Moon about its planet is approximately circular, with a mean radius of 2.18 × 10^8 m. It takes 31.2 days for the Moon 
to complete one revolution about the planet. 
Find the mean orbital speed of the Moon. 
Answer in units of m/s 

Find the Moon’s centripetal acceleration. 
Answer in units of m/s^2

Answer 1

Given

Radius of orbit is  r = 2.18 × 10^8 m

Revolution time is 31.2 days =  31.2 × 24 × 60 × 60

                                            = 2695680 ⇒ 2.69 × 10^6 s

Perimetre of moons orbit = 2π r

                                        = 2 × π × 2.18 × 10^8 

                                        = 1.369 × 10^9 m

Mean orbital speed of the Moon,v = perimetre / revolution time 

                                               = (1.369 × 10^9) / (2.69 × 10^6)

                                               =508.12 m/s

 

Moon’s centripetal acceleration ac    = v²/r

                                                =  (508.12)² / 2.18 × 10^8

                                                = 0.0012 m/s²