Shock Waves and Sonic Boom!!
What is the Mach Number?
Table of Contents:
It’s a lazy Sunday. You are lying on your bed and chatting with your best friend.
But suddenly, out of nowhere, your mom appears in front of you! When did she come in? What a shock!!! This is something that happens with the sound waves too! Let’s understand what and how shock waves are created. Before actually getting into Shock waves we need to understand a few basic terminologies, let’s get into it first!
Shock Waves:
The velocity of Sound:
When we speak, we produce longitudinal waves, which create regions of compression and rarefaction alternatively. This is how sound travels, in compression and rarefaction alternate waves. The speed of sound is 340.29 m/s.
Mach Number:
Mach number is the ratio of inertial force to elastic force, when it is further deduced, it can be written as the ratio of object speed to speed of sound. The Mach Number is important because it tells us how the object will be affected by the presence of fluid in the surroundings.
Case 1: Subsonic (Mach No. < 1.0)
When Mach Number is less than 1, or when the speed of the object moving is less than the speed of sound, it is called a Subsonic condition.
Let’s consider the same example that we were discussing before. Imagine you are sitting in your room and chilling out. You hear your mom’s footsteps approaching your room. Mom opens the door, you wave her hi!
In this case, you were prepared that someone is approaching you as you heard the footsteps. On similar lines, you can imagine, when the sound waves travel slower than the moving object, the sound waves are prepared for the approaching object. The sound waves are expecting some object to pass through and the object arrives.
Case 2: Sonic (Mach No. = 1.0)
When Mach Number is equal to 1, or when the speed of the object moving is equal to the speed of sound, it is called Sonic condition.
Again imagine the same example. You are sitting in your room and chilling out. But this time you could not hear your mom approaching you. Suddenly out of nowhere, you heard someone opening your room’s door. Obviously, you were in a shock for few seconds, because you were not prepared for it.
Similarly, you can imagine, when the speed of the object is equal to the speed of sound, the sound waves are not ready for the object approaching. The sound waves had no idea that the object was entering its zone. Hence, the shock waves are created and these shock waves impact the object.
Case 3: Supersonic (Mach No. > 1.0)
When Mach Number is greater than 1, or when the speed of the object moving is greater than the speed of sound, it is called a Supersonic condition.
This time, you are sitting in your room and suddenly, someone is standing in from of you. That is a real terror, isn’t it!
Similarly, if the object speed is greater than the speed of sound, greater shock waves and impact is created.