I'm having trouble with the correct setup for the following problem: A physics student, who likes physics experiments, dangles her watch from a thin piece of string while the jetliner she is in takes off from JFK Airport. She notices that the string makes an angle of 25 degrees with respect to the vertical as the aircraft accelerates for takeoff, which takes about 18 seconds. Estimate the takeoff speed of the aircraft. Given: Theta = 25 degrees ; time = 18 s Unknown: Ft, acceleration (ax and ay) I drew an FBD and split up gravity into its x and y components. I have the equations as: mg sin 25 = m ax Ft - mg cos 25 = m ay What's wrong with this approach?