To create a formula calculate the mass of the pipe need to know the cross-sectional area of a hollow cylinder. To do this, must be a known wall thickness (a). If the conditions of the problem it is not, but the internal (d) and outer (D) diameters, we define the thickness of the walls through half the difference of these quantities: a = (D-d)/2. The cross-sectional area define as multiplied by the number of PI the difference between the work external diameter to the wall thickness and the square of the thickness of the walls: π*(D*a-a2).
Using the formula cross-sectional area, determine the volume that is enclosed between the outer and inner walls - multiply the obtained in the previous step, formula for length (L) of the pipe: π*(D*a-a2)*L.
To get the final formula for calculating the mass (m) of a hollow cylinder, it remains to consider the material from which the pipe is made. To do this, multiply the formula from the previous step for the density (ρ): m = π*(D*a-a2)*L*ρ.
Substitute into the formula the values given in the conditions of the problem, and calculate the result. In this case, consider the dimension of the input variables. For example, the outer diameter of the steel pipe is 30 cm, the wall thickness is 5 mm, a length of 4 m and density of steel - of 7.95 g/cm3. In this case, you can substitute in the formula all values in centimeters, to get the result in grams and convert it to kilograms: 3,14*(30*0,5-0,52)*400*7,95 = 3,14*14,75*400*7,95 = 147281,7 g ≈ 147,3 kg.
In practical calculations to determine the values of the variables that you want to substitute in the formula, use the marking on the pipe or as specified in the accompanying documents. Knowing her, to determine the desired value is possible according to the normative documents - state Standards. For example, the density of the steel pipes can be learned from GOST 9941-8, and the density of plastic is given in GOST 18599-2001.
If you only need approximate values, you can use the online calculators- a reference to one of them below. This service allows you to calculate the mass of the tubes of the eight types of metals.