# Plastic pipe

Calculate weight of the plastic pipe with diameter d = 70 mm and length 380 cm if the wall thickness is 4 mm and the density of plastic is 1367 kg/m3.

Result

m =  4.3 kg

#### Solution:

$r_1 = d/2 = 35 \ mm \ \\ r_2 = r_1 -4 = 31 \ mm \ \\ V = V_1 - V_2 = \pi r_1^2 l - \pi r_2^2 l \ \\ V = \pi l ( r_1^2 - r_2^2 ) = 3151.65 \ mm^3 \ \\ m = \rho V = 1367 kg/m^3 \cdot 3151.65 \ mm^3 = 4.3 \ \text { kg }$

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