Cracking Your Knuckles When you \"crack\" a knuckle, you cause the knuckle cavit
ID: 2199706 • Letter: C
Question
Cracking Your KnucklesWhen you "crack" a knuckle, you cause the knuckle cavity to widen rapidly. This, in turn, allows the synovial fluid to expand into a larger volume. If this expansion is sufficiently rapid, it causes a gas bubble to form in the fluid in a process known ascavitation. This is the mechanism responsible for the cracking sound. (Cavitation can also cause pits in rapidly rotating ship's propellers.)
Explanation / Answer
0 dB is the threshold of hearing the dB scale is defined by dB = 10 log(I/I0) where I0=10^(-12) W/m^2 and is the threshold of hearing so we want to figure out how far away you have to be so this intensity is 0dB or 10^(-12)W/m^2 58 dB has an intensity: 58=10log(I/10^(-12)) where I is the intensity of the crack and log is a base 10 log 5.8=log(I/I0) 10^(5.8)=I/10^(-12) =>I = 10^(-6.2)=6.3x10^(-7) this intensity is 6.3x10(-7)/10^(-12) =6.3x10^5 times greater than the threshold intensity since intensity of sound varies as 1/r^2, we need to move 794 times farther away (since 6.3x10^5/794^2=1). this means you can hear the sound 794x16cm=12704 cm or 127m away !!!!!