1.During a test flight in which a 9000-kg helicopter starts from rest at t = 0, the acceleration of its center of mass from t =0 to t =10 s is a=(0.6t)i+ (1.8 ? 0.36t)j m/s2. What is the magnitude of the total external force on the helicopter (including its weight) at t = 6 s?
2.Given a mean earth radius of 20,906,000 ft, and an observation latitude of N 33 degrees, what is the arc distance of one second of longitude and one second of latitude?