Calculate volume and surface area of a boiler

[scientist]

Homework Statement

A boiler drum is equipped with hemispherical heads (i.e. the two heads together make a sphere.) The diameter of the drum is 0.8 meters and the drum is 5 meters in length.

Calculate: a.) The area of insulation required to cover the entire drum.
b.) The total volume of the drum.

Homework Equations

Cylinder total surface area = (2)(pi)(r)(h) + (2)(pi)(r²)
Sphere total surface area = (4)(pi)(r²)
Cylinder volume = (pi)(r²)(L)

The Attempt at a Solution

answers

a) i) Cylinder total surface area = (2)(pi)(r²)(h) + (2)(pi)(r² )
= (2) (3.14) (0.4)(5m) + (2)(3.14) (0.4)²
= 12.56 m² + 1
= 13.56 m² insulation required to cover the drum.

ii) Sphere total surface area = (4)(pi)(r²)
= (4) (3.14) (0.4)²
= 2 m² insulation required to cover the two heads.

iii) Total surface area i+ ii = 13.56 m² + 2 m²
= 15.56 m² total insulation required to cover the entire drum.

b) Cylinder volume = (pi)(r²)(L)
= (3.14)(0.42)(5m)
= 2.5 m² total volume of the drum.

How does my answer look?

 

[Delphi51]

total surface area = (2)(pi)(r2)(h) + (2)(pi)(r2 )

Drop the second term! There are no ends on the cylinder; they have been replaced by the hemispheres. And where did the r2 come from? Just r. By the way, you can easily copy symbols like the square ² from my signature or here:
https://www.physicsforums.com/blog.php?b=346

total surface area = (2)(pi)(r)(h) + (4)(pi)(r² )