Question

Find the mass of a 3.5 m long lead pipe, if the external diameter of the pipe is 2.4 cm, thickness of the metal is 2 mm and the mass of 1 cm³ of lead is 11.4 grams.

Answer 1

Length of the pipe (h) = 3.5 cm = 300 cm

External radius of the pipe (R) =  \[\frac{2 . 4}{2} = 1 . 2 cm\]

 Thickness of pipe = 2 mm

                              = 0.2 cm

So internal radius of pipe = 1.2 - 0.2

                                          = 1cm

Thus volume of pipe `=pi(R^2 - r^2)h`

`=22/7 xx ((1.2)^2 - 1^2) xx 300`

`=22 xx 50 xx 0.44 cm^3`

`=484 cm^3`

Mass of 1 cm³ pipe is 11.4 gm

Total mass = 4184 × 11.4 = 5517.6 gm = 5.518 kg.