A hollow iron pipe is 2.1m long and its external diameter is 4.5 cm.if the thickness of pipe is 0.25cm and weight of iron is 4 gm/cm3, then the weight of pipe is? (ans 2.805kg) ?

Answer 1

The outer radius R=2.25 cm
The inner radius r=2.25-0.25 = 2.0cm

So, the volume of pipe is

2.1 * π(R^2-r^2)
= 210cm * π(2.25^2-2^2)cm^2
= 701 cm^3

Now you can get the mass of the pipe.