heights and distances

Let the speed of the jet plane be V in m/s and X be the initial horizontal distance of jet plane from the observer.

D, the distance it travels in 8 seconds = 8V.

tan 60 = 18003/X

or X = 18003/tan 60 = 1800 m

The horizontal distance, X increases by D = 8V in next 8 seconds and the angle of elevation becomes 45.

Hence,

tan 45 = 18003/(X+8V)

X + 8V = 18003/tan 45 = 18003

8V = 1800x1.73 - X = 1800x0.73 = 1314 m

V = 1314/8 = 164.25 m/s

Regards,

Team,

TopperLearning.