Question

The thickness of a metallic tube is 1 cm and the inner diameter of the tube is 12 cm find the weight of 1 metre long tube is the density of the metal be 7.8 gram per centimetre cube

Answer 1

cross section ... (π / 4)[(do)^2 - (di)^2]

volume = cross section * length

mass = volume * density

weight = m g

Answer 2

Area of circle:

A = d² π / 4


Inner diameter:

d1= 12 cm

Outer diameter:

d2 = d1 + 2 ∙ thickness

d2 = d1 + 2 ∙ 1 = 12 + 2 = 14 cm


Area of ring:

A = ( d2² - d1² ) ∙ π / 4

A = ( 14² - 12² ) ∙ π / 4

A = ( 196 - 144 ) ∙ π / 4

A = 52 ∙ π / 4

A = 13 π cm²


1 m = 100 cm

Volume:

V = A ∙ L

V = 13 π ∙ 100

V = 1300 π cm³


ρ = density

Weight:

w = V ∙ ρ

w = 1300 π ∙ 7.8 = 1300 ∙ 3.14159 ∙ 7.8 = 31 855.7226 gr


1kg = 1000 gr

w = 31.8557226 kg