A cylindrical gas container is closed at the top and open at the bottom.
If the iron plate of the top is (5)/(4) times as thick as the plate forming the cylindrical sides, find the ratio of the radius to the height of the cylinder using minimum material for the same capacity.
Show Hint
For minimum material problems, express surface area in terms of one variable using volume constraint.
Let radius =r, height =h.
Step 1: Volume fixed:
V=π r²h
Step 2: Material used:
M=2π rh + (5)/(4)π r²
Step 3: Using h=(V)/(π r²) and minimizing M w.r.t. r,
we obtain:
(r)/(h)=(2)/(3)
Hence, required ratio is (2)/(3).