Flying Circus of Physics When you \"crack\" a knuckle, you suddenly widen the kn
ID: 1506214 • Letter: F
Question
Flying Circus of Physics When you "crack" a knuckle, you suddenly widen the knuckle cavity, allowing more volume for the synovial fluid inside it and causing a gas bubble suddenly to appear in the fluid. The sudden production of the bubble, called 'cavitation', produces a sound pulse - the cracking sound. Assume that the sound transmitted uniformly in all directions and that it fully passes from the knuckle interior to the outside, at a distance of 0.29 m from your ear. If the pulse has a sound level of 62 dB at your ear, what is the rate at which energy is produced by the cavitation?Explanation / Answer
sound level = 10* log10(I/10^-12)
62.0 = 10 log 10 (I/10^-12)
10^(6.2) * 10^-12 = I
I = 1.58 * 10^-6 W/m^2
Intensity = Power/ Area
I = P/(4r)^2
Substituing Values,
1.58 * 10^-6 =P/(4(0.29)^2)
P= 1.67 * 10^-6 W