Posted by sona on .
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

maths 
sona,
Area of a circle = ðr²
Inner diameter = 12 cm
Inner radius = 6 cm
Outer radius = 6+1 = 7 cm
Cross sectional area of an annulus (ring)
= ð(r2²r1²)
=(7²6²)ð
=13ð cm²
Volume for a 1 metre tube:
V=13ð&100cm cm³
=1300 cm³
Mass ("weight")
=volume * density.