A hollow iron pipe is 28 cm long and its external diameter is 10 cm. If the thickness of the pipe is 2 cm and iron weighs 5g/cm3, then the weight of the pipe is :
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 7040 g
External radius of pipe = 10/2 = 5 cm
if thickness is 2cm then inner radius = (10 - 4)/2 = 3 cm
Let R and r be external and inner radius of hollow pipe respectively
volume of hollow cylinder = πR2h - πr2h
where h = height
volume of pipe = πh(R2 - r2)
22/7 × 28 (52 - 32)
22 × 4 × 16 = 1408 cm3
If iron weighs 5g/cm3, then the weight of the pipe = 1408 × 5 = 7040 g