What is the relationship between diameter and mass per length in a steel wire?

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The relationship between diameter and mass per length in a steel wire is influenced by the wire's density and cross-sectional area. The density of steel is given as 7860 kg/m³, but to find mass per unit length, the cross-sectional area must be considered, which is related to the diameter. A larger diameter results in a greater cross-sectional area, leading to increased mass per length, assuming uniform density. The discussion emphasizes the need to convert density from mass per volume to mass per length by incorporating the wire's diameter. Understanding this relationship is crucial for solving related physics problems.
nesan
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Homework Statement



http://puu.sh/frpk5/eae7bce2e3.png

Homework Equations



v = sqrt(T / (m / L));

The Attempt at a Solution



7.86 g / cm^3 = 7860 kg / m^3

T = v^2 * m/L

T = 160 ^ 2 * 7860 which is a huge number

I have no idea where the diametre plays a part.
 
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m/L ≠ 7860 (check the dimensions)
 
Nathanael said:
m/L ≠ 7860 (check the dimensions)
I'm sorry I really don't understand what you're aiming at. Does it have to do with the m^3?

I know it's mass per unit length but how would I go from 7860 kg / m^3 to what I need? Thank you.
 
nesan said:
I'm sorry I really don't understand what you're aiming at. Does it have to do with the m^3?
You were given the mass per volume, but you want to know the mass per length. You used the mass per volume where you should have used the mass per length.

nesan said:
I know it's mass per unit length but how would I go from 7860 kg / m^3 to what I need? Thank you.
Consider a steel wire with a larger diameter. (They are both steel, so the density is the same.) Which one will have the larger mass per length? Or will it be the same? And why?
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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