1. The problem statement, all variables and given/known data A friendly Brazilian has a mass of 150 kg. Being in Brazil, he rotates in a circle around the center of the earth once per day, The radius of this circle (which is essentially the radius of the Earth) is 6.40 x 10^6 m. I have found that the normal force is 1.4649 x 10^3. 2. Relevant equations ac = v2/r , centripetal acceleration [itex]\Sigma[/itex]F=ma v = (2[itex]\pi[/itex]r)/T , T is period of one revolution 3. The attempt at a solution I only got to mg - Fn = mac I know what the apparent weight is but I'm not sure about the normal force. If I can find this, then I can then find ac, v, and then T to find about the length of day.