Question

the angle of elevation of an aeroplane from a point P on the ground is 60degree.After a flight of 15seconds the angle of elevation changes to 30degree,.if the aeroplane is flying at a constant height of 1500root3.find the speed of the aeroplane in Km/hr

Answer 1

tan60=BE/AB
√3 =1500√3/AB
AB=1500m

tan30=CD/AC
1/√3=1500√3/AC
AC=4500m

BC =AC-AB
BC=4500-1500
BC=3000m

Speed in m/sec = 3000m/15sec
speed =200m/s
speed in km/hr=720km/hr