Respuesta :
Answer:
L = 0.7 m
Explanation:
This is a resonance exercise, in this case the air-filled pipe is open at both ends, therefore we have bellies at these points.
λ / 2 = L 1st harmonic
λ = L 2nd harmonic
λ = 2L / 3 3rd harmonic
λ = 2L / n n -th harmonic
the speed of sound is related to wavelength and frequencies
v =λ f
f = v /λ
we substitute
f = v n / 2L
the speed of sound in air is v = 343 m / s
suppose that the frequency of f = 980Hz occurs in harmonic n
f₁ = v n / 2L
f₂ = v (n + 1) / 2L
f₃ = v (n + 2) / 2L
we substitute the values
2 980/343 = n / L
2 1260/343 = (n + 1) / L
2 1540/343 = (n + 2) / L
we have three equations, let's use the first two
5.714 = n / L
7.347 = (n + 1) / L
we solve for L and match the expressions
n / 5,714 = (n + 1) / 7,347
7,347 n = 5,714 (n + 1)
n (7,347 -5,714) = 5,714
n = 5,714 / 1,633
n = 3.5
as the number n must be integers n = 4 we substitute in the first equation
L = n / 5,714
L = 0.7 m
