Question

the thickness of a metallic tube is 1 cm and the inner diameter of tube is 12 cm . Find the weight of 1 meter tube long, if the density of metal be 7.8 gram/cm^3

Answer 1

Area of a circle = πr²

Inner diameter = 12 cm
Inner radius = 6 cm
Outer radius = 6+1 = 7 cm

Cross sectional area of an annulus (ring)
= π(r2²-r1²)
=(7²-6²)π
=13π cm²

Volume for a 1 metre tube:
V=13π&100cm cm³
=1300 cm³

Mass ("weight")
=volume * density.