The angle of elevation of a jet plane from point A on the ground is 60˚. After A flight of 15 seconds, the angle of elevation changes to 30˚. If the jet plane is flying at a constant height of 1500 √ 3 m, find the speed of the jet plane.

Question

Philoid · Accepted Answer

Let the jet plane goes from point P to point C and we have given,

Initially angle of elevation from point A, ∠PAQ = θ₁ = 60°

After 15 seconds,

Angle of elevation from point A, ∠CAB = θ₂ = 30°

As the plane is flying at a constant height,

BC = PQ = 1500√3 m

Now,

In ΔABC

In ΔAPQ

So, we have

QB = AB – AQ = 4500 – 1500 = 3000 m

And

QB = PC

So, jet plane travels 3000 m in 15 seconds

And we know,