There are classical examples of sonic booms being found in low-tech objects, for example, the crack of a whip's tail. I am wondering if clapping hands is a manifestation of sonic booms in some form, or a heavy paperback book dropping on a flat smooth floor. Assume one hand clap is nearly airtight and releases only 1 cc of air. Then, that is about 10^-6 kg, or 1 mg of mass. On a first order consideration, an arm is 1 kg in mass, with the tangential motion considered linearly. We further specify a hand velocity of 5 m/s. Then, if the energy of the hands is totally transferred to the air, one can expect about \(sqrt(2000000) ~= 1440\) times the velocity of the hand, or about 7200 m/s. This estimate is obviously way too large, since most of the energy is absorbed by the hand tissue (collagen, what have you) in a largely inelastic (viscoelastic) collision. But that should leave plenty of room for a residual sonic boom, right?
As its name suggests, the sonic boom can only be produced when something moves faster than the speed of sound. I highly doubt that any part of our hands or any falling book will reach the speed of sound.
Of course not. Facial is suggesting that the air squeezed from between your hands, or from under the book may be forced out sideways faster than the speed of sound. Could be right, for all I know. On a similar crazy note, perhaps clicking your fingers is separating them fast enough that a small pocket is vaccuum is left that the air fills with pop. (I'd be surprised if that were true... but it would be pretty cool.)
He is not suggesting that the hand or book breaks the sound barrier, he is suggesting that the air involved in the process is displaced fast enough to break the sound barrier, presumably suggesting that this creates a mini shock wave which gives rise to the 'crack' kind of sound you get. I sort of doubt it since the sound doesn't really change qualitatively as you clap harder for instance. There isn't a point where the clap goes from being a muffled thud to a loud crack, it seem continuous to me. I don't think you could really call it a sonic boom anyway, you don't call the shockwave caused by an explosion a sonic boom. Actually I don't know, maybe if you clap really hard the compression wave could become a real shock wave. Somehow I don't think so though.
This is interesting- I just tried it, and I think there is a gradual shift as well. It could be a sub-sonic acoustic wave. Whereas, the crack of a whip is more dichotomous.
I still think it would take a lot more than clapping hands or a falling book to make a parcel of air travel any distance at 340 m/s. The speed of the hands themselves are only a few meters per second so I would imagine the air gets pushed out at most an order of magnitude faster but not coming close to the speed of sound. You could argue that slapping anything which makes a noise could cause a mini sonic boom but I just don't believe it, sorry.
It is the mark of an educated mind to be able to entertain a thought without accepting it. (Commonly attributed to Aristotle) It doesn't matter what we believe about it. I don't necessarily believe it either. But that doesn't stop me considering it. You've had a quick guess at a couple of variables, which is good. If you move your hands at a few metres per second when clapping... (How many m/s? More than 1, less than 100? Maybe 10? Could you measure it?) ...and the sideways displacement of air is an order of magnitude higher... (Is this purely a guess? What affects that value? Why 10 times? Why not 1, or 100?) ...then we have air moving at 100m/s, which is 1/3 the speed of sound in air. That's not that far off. To me, it doesn't rule out the possibility under consideration at all.
That's OK, because I have also considered it and came to the conclusion that it's highly unlikely. I would say at most 2 m/s. There are many variables that would affect it but from intuition alone, I would imagine that it would be a rare combination of these variables that would cause air to shoot out at more than 300 m/s from hands that are clapping at 2m/s. Intuitively there is not enough energy in the system to cause a parcel of air to have enough energy to cause a sonic boom. Perhaps my intuition is wrong though and you will give me an example of a slow moving system which displaces about the same amount of air as a human hand clap at a speed faster than sound?
I have an intriguing and important question: with a properly sized anus and high air flow, could you create a sonic boom from a fart?
