Question

The angle of elevation of an aircraft from a point on horizontal ground is found to be 30 degree. After 24 secs it's elevation found to be 60 degree. If the height of the aircraft from the ground is 3600√3 metre, find the velocity of the aircraft.?

Answer 1

Let the position of the observer be at A. The positions of aircraft are C and D respectively in the horizontal level at the height of `3600sqrt3` m.

Hence `BC=FD=3600sqrt3` m

Now

`AB=BCcot30^@=3600sqrt3*sqrt3=10800`m
Similarly

`AF=FDcot60^@=3600sqrt3*1/sqrt3=3600`m

So displacement (d) of the aircraft during time `t=24` s will be `d=AB-AF=10800-3600=7200` m

Hence velocity of the aircraft

`v=d/t=7200/24=300` m/s