Question

The thickness of a metallic tube is 1 cm and inner diameter of the tube is 12 cm. Find the mass of 1 m long tube, if the density of the metal be 7.8 gm/cm${}^3$

• A.
  31459.60 gm
• B.
  32349.60 gm
• C.
  31839.60 gm
• D.
  31843.60 gm

Answer 1

The correct option is C

31839.60 gm

Here, r = 6cm, R = 7cm, h = 100 cm
Volume of given tube = $\pi h(R^2-r^2)$
= $3.14\times 100\left(\right(7{)}^2-\left(6{)}^2\right)$
= $314\times (49-36)=314\times 13$
= 4082 cm${}^3$

Mass = volume $\times$ density
= 4082 cm${}^3\times$ 7.8 gm/cm${}^3$
= 31839. 60 gm