See image below for detailed explanation
Answer:
length = 1.24m
Explanation:
velocity = frequency x wavelength
wavelength = velocity/frequency
w = 343/69 =4.97m
length = wavelength/4
length =4.97/4 =1.24m
Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction on that system. Mathematically can be written as,

Here,
v = speed of the exhaust gases measured relative to the rocket.
= Rate of change of mass with respect to time
Our values are given as,


Replacing we have that


Dipper effect of an oncoming train get louder as it approaches and sound diminishes as it goes away sound traveling