Question

the length of a metallic tube is 1 metre , it's thickness is 1 cm and it's inner diameter is 12cm . find the weight of the tube if the density of the metal is 7.7 grams per cubic centimetres,

Answer 1

Area of a circle = ðr² 
Inner diameter = 12 cm 
Inner radius = 6 cm 
Outer radius = 6+1 = 7 cm 
Cross sectional area of an annuls (ring) 
= ð(r2²-r1²) 
=(7²-6²)ð 
=13ð cm² 

Volume for a 1 meter tube: 
V=13ð & 100
=1300 cm³ 

Answer 2

inner diameter = 12 cm

Therefore, radius = 6 cm

Thickness = 1 cm

External radius = thickness + inner radius

=1 + 6 = 7 cm.

Length of tube = 1 m = 100 cm

Now, volume of tube = π(R² - r²)h

22/7 * (7² - 6²) * 100

22/7 * 13 * 100 = 4085.71 cm³

Density of metal per cm³ = 7.7 g

Weight of tube = 7.7 g × 4085.71

                         = 31868.538 g

                         = 31.868 kg