An aeroplane is going towrds east at a speed of `510 kmh^-1` at a height of2000 m. At a certain instant, the sound o theh plane heard by a ground obserger appears to come from a point vertically above him. Where is the plane at this instant? Speed of sound in air `=340 ms^-1`

Explanation

The situation is shown in figure-6.7. The sound reaching the ground observerP, was emitted by the plane when it was at the point Q vertically abovehis head. The time taken by the sound to reach the observer is
`t = (2000)/(340) = (100)/(17)s`

The distance moved by the plane during this period is
d = vt
= `(510xx5)/(18) xx (100)/(17)`
= 833.33 m
Thus, the plane will be 833.33 m ahead of the observer on itsline of motion when he hears the sound coming vertically to him