Question

an iron pipe is 21 m long and it's exterior diameter is 8 cm .if the thickness of the pipe is 1 cm and iron weight is 8 g /cm find the weight of pipe

Answer 1

External radius = 4 cm Internal radius = 3 cm Volume of iron = 227×42-32×21cm3= 462cm3 Weight of iron = (462 x 8)gm = 3696 gm = 3.696 kg

Answer 2

Given:

Length of pipe=21m

External diameter=8cm

Thickness of pipe=1cm

Weight of iron=8g/$cm^{3}$

To Find:

Weight of the pipe

Solution:

• Internal radius=(4-1)cm=3cm
• External Volume:

      $(\dfrac{22}{7}\times4\times 4\times 4)$$cm^{2}$

       =1056$cm^{2}$

• Internal Volume:

     = $(\dfrac{22}{7}\times3\times 3\times 21)cm^{2}$

     =594$cm^{2}$

• Volume of the metal=(external volume)-(internal volume)

      =(1056-594)$cm^{2}$

      =462$cm^{2}$

• Weight of the pipe:

    =$(462\times 8)$g

    =$(\dfrac{462\times 8}{1000})$kg

    =3.696kg

• ∴Weight of the pipe is 3.696 kg