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Thread moved from the technical forums to the schoolwork forums

I saw the following problem in a test I was reviewing:

I don't understand how they got their answer. I used the formula: ƒ=sqrt(T / u) / 2L where f is the frequency of the string, T is the tension, u is the linear mass density, and L is the length of the string.

I got:

T = mg = 50 * 9.8 = 490N

u = m/l = 3/7 g/cm = 0.04285 kg/m

L = 70cm = 0.7m

Therefore f = sqrt(490 / 0.04285) / 1.4 = 106.93 / 1.4 = 76.38Hz. I see that they got their answer from the first part, but did they forget to divide by 2L, or was I not supposed to do that? Thanks!

I don't understand how they got their answer. I used the formula: ƒ=sqrt(T / u) / 2L where f is the frequency of the string, T is the tension, u is the linear mass density, and L is the length of the string.

I got:

T = mg = 50 * 9.8 = 490N

u = m/l = 3/7 g/cm = 0.04285 kg/m

L = 70cm = 0.7m

Therefore f = sqrt(490 / 0.04285) / 1.4 = 106.93 / 1.4 = 76.38Hz. I see that they got their answer from the first part, but did they forget to divide by 2L, or was I not supposed to do that? Thanks!