Physics Assignment Answers
Chapter 6 - Newton's 3rd Law
You are in free fall, of course. Less abstractly, suppose you have a mass of 60 kg and a weight (= mg) of about 600 Newtons, which is the net force on you. Your acceleration when you step off a ledge, a = Fnet/m = (600 N)/(60 kg) = 10 m/s2.
The Earth accelerates upward because the net force on the Earth (assuming that you are the only object interacting with the Earth at this moment) is the Newton's Third Law reaction force "you pull Earth," which equals your weight also (since Newton's Third Law action/reaction forces are always exactly the same size). The acceleration of the Earth, then is:
The Earth has a mass of about 6 x 1024 kg. If you have a mass of 60 kg, this gives an acceleration for the Earth of about:
No wonder you don't notice it!