Question

A supersonic plane flies directly over you at 1.8 times the sound speed. You hear its sonic boom 20s later.
What is the plane's altitude, assuming a constant 340 sound speed?

Answer 1

height= velocity sound*time

Answer 2

The angle that the bow shock wave makes with the velocity vector, and with the ground, is
A = sin^-1 (1/M) = 33.8 degrees.

The relationship between altitude h and sonic boom delay time t is:
h/(Vt) = tan A = 0.668
where V = airplane speed = M*Vsound = 612 m/s

Thus
h = 0.668 v t = 818 m

BobPursley's formula would result in
680 m.

The shock wave cone behind the airplane moves faster than the speed of sound.