Determine the length of a copper pipe if the sound from a blow at one end of the pipe is heard

| October 8, 2021 | education

Determine the length of a copper pipe if the sound from a blow at one end of the pipe is heard at the other twice with an interval of 0.9 s. The speed of sound in air is 340 m / s, and in copper 3400 m / s

Δt = 0.9 s.

Vv = 340 m / s.

Vm = 3400 m / s.

S -?

Sound is a mechanical wave that travels through the air and copper pipe.

Since the speed of sound propagation in copper Vm is greater than in air Vv, sound propagates through a copper pipe earlier than through air. Therefore, the sound from the impact is heard twice.

Δt = tv – tm, where tv is the propagation time of sound from a shock in the air, tm is the propagation time of sound from a shock in a copper pipe.

tv = S / Vv, tm = S / Vm, where S is the length of the pipe.

Δt = S / Vv – S / Vm = S * (Vm – Vv) / Vw * Vm.

S = Vv * Vm * Δt / (Vm – Vv).

S = 340 m / s * 3400 m / s * 0.9 s / (3400 m / s – 340 m / s) = 377.8 m.

Answer: a copper pipe has a length of S = 377.8 m.



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