Francesca, who likes physics experiments, dangles her watch from a thin piece of string while the jetliner she is in takes off from Dulles Airport . She notices that the string makes an angle of 25° with respect to the vertical while the aircraft accelerates for takeoff, which takes about 13.5 seconds. Estimate the takeoff speed of the aircraft. (m/s)
(See attachment for full question)
Horizontal force= m a
where a is the acceleration
Vertical force = weight = mg
tan 25 = ma / mg = ...
The solution calculates takeoff speed of the aircraft.