Brain Post: How a Sonic BOOM Works | Yes, A Bullwhip “Snap” is a Sonic Boom

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A sonic boom in a jet
F-22 Raptor breaking the sound barrier.

The sonic boom is something that most people have difficulty understanding.  This difficulty arrises from the fact that it’s tough to visualize.  We are gonna try to break it down for you in the simplest term with some visual cues to help it stick.  (or just skip down to the NASA video that explains it well)

THE SONIC BOOM:

1. A sonic boom occurs anytime an object is traveling faster than the speed of sound (about 600-760 mph depending on air density).  Lets think of a jet plane.

2.  When the jet passes through the air it creates a series of pressure waves in front of it and behind it as it travels.  These pressure waves are similar to the waves created by the bow and stern of a boat.

Bow wave and pressure wave
Bow wave (top) and pressure wave (bottom)

3.  “These waves travel at the speed of sound, and as the speed of the jet increases, the waves are forced together, or compressed, because they cannot get out of the way of each other, eventually merging into a single shock wave at the speed of sound.” – wikipedia

the rings represent pressure waves

4.  Ok, the above image really helps:

– 1st image (Ma < 1) is less than the speed of sound.

– 2nd image (Ma = 1) is right at the speed of sound.

– 3rd image is faster than the speed of sound (the red line is where the boom would be heard)

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 Skip to 2:22 for the explanation of the sonic boom

5.  What EXACTLY causes the boom is THIS:  

A- There is a rise in air pressure at the nose of the plane (from the plane pushing on the air as it goes forward)

B- Then the air pressure immediately goes back to normal after the plane passes that air.  

C- The “boom” occurs when there is a sudden change of pressure.  So, there are actually two booms in a sonic boom (sounds like one):  1- initial sudden air pressure rise from the nose pushing against the air, 2- air pressure suddenly returns to it’s normal pressure right after the plane passes it.

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 Get it?  Tell us in the comments.  This is a tough one to explain and to fully understand.  Full Details of the Sonic Boom

bull whip
bull whip

BULL WHIP = SONIC BOOM

– I don’t think people would believe me about this, so I’ll have wikipedia do the talking:

“The cracking sound a bullwhip makes when properly wielded is, in fact, a small sonic boom. The end of the whip, known as the “cracker”, moves faster than the speed of sound, thus creating a sonic boom.[6] The whip is probably the first human invention to break the sound barrier.

A bullwhip tapers down from the handle section to the cracker. The cracker has much less mass than the handle section. When the whip is sharply swung, the energy is transferred down the length of the tapering whip. In accordance with the formula (if the work for whipping remains constant) forkinetic energy E_k = {mv^2}/{2}, the velocity of the whip increases with the decrease in mass, which is how the whip reaches the speed of sound and causes a sonic boom.” – wikipedia

 


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2 thoughts on “Brain Post: How a Sonic BOOM Works | Yes, A Bullwhip “Snap” is a Sonic Boom

  1. what a load of bull dust . I can crack my washing when I flick out the creases before I fold it .. I think any woman could tell you that or any kid that has flicked there mate with a bath towel ..and know mater how fast i move a tea towel i am sure it is not up in the 500k mark

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