Question

the angle of elevation of a jet plane from point a on the ground is 60 degree after a flight of 30 seconds the angle of elevation changes to 30 degrees at the jet plane is flying at a constant height of 3600 root 3 find the speed of a jet plane

Answer 1

Let us suppose that

CD = y and DE = x

Now from triangle BED

tan 60 = BD/DE

=> √3 = 3600√3/x

=> x = 3600

Again from triangle ACE

tan30 = AC/CE

=> 1/V3 = 3600V3/CE

=> CE = 3600V3*V3

=> CE = 3600*3

=> CD + DE = 10800

=> x + y = 10800

=> 3600 + y = 10800

=> y = 10800 - 3600

=> y = 7200

Now from figure

AB = CD = 7200

So speed = distance/time

=> speed = 7200/30 = 240 m/s = 240 * (18/5) km/h

{If we convert m/s into km/h, we multiply 18/5, So 240 m/s = 240 * (18/5) km/h}

=> speed = 48 * 18 = 864 km/h

So speed of the aeroplane is 864 km/h