You will need
  • knowledge of the linear density or the density of the material
Units of mass are converted to units of length by using a physical quantity called linear density. In the SI system it has the dimension of kg/m As can be seen, this value differs from the usual density that expresses the mass per unit volume.
Linear density is used to characterize the thickness of threads, wires, fabrics, etc., as well as for the characterization of beams, rails, etc.
From the definition of linear density, it follows that for the translation of the mass in the length needed to divide the weight in kilograms per linear density in kg/m. thus we obtain the length in meters. In this length and will be given weight.
In that case, if we know the normal density with the dimension kg per cubic meter, to calculate the length of the material, which contains a mass, divide mass by density, and then to the cross-sectional area of the material. Thus, the formula for the length would be: l = V/S = (m/p*S) where m is the mass and V is the volume containing the mass, S is the cross - sectional area, p is the density.
In the simplest cases the cross section of the material will have either a round or rectangular shape. The area of the circular section is equal to pi*(R^2), where R is the radius of the cross section.
In the case of rectangular cross section, its area is equal to a*b, where a and b are the lengths of the sides of the section.
If the cross-section has a non-standard form, in each case, you need to find the area of the geometric shape that represents the cross-section.