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Sagesky
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Homework Statement
To reduce heat loss, the surface area of a hot-water tank must be kept to a minimum. If such a tank is 125 litters in capacity, and can be approximated by a cylinder in shape with a hemispherical end cap; calculate the radius and overall height for minimum heat loss.hi can anyone check my ansers please thanks
The Attempt at a Solution
125 litres = 125000 cm^3
The volume is the sum of the volume of a hemisphere and a cylinder.
V= 2/3 πr^3+πr^2 h
The surface area is
S=2πrh+2πr^2
Isolate h in the Volume equation.
V= πr^3+πr^2 h
h=(V- 2/3 πr^2 )/(πr^2 )
Substitute for h into the Surface area equation.
S=2πr^2 (V- 2/3 πr^2 )/(πr^2 )+2πr^2
S=(2V )/r+2/3 πr^2
calculate the derivative.
ds/dr= - (2V )/r^2 +4/3 πr
Solve for r
- 2V + 4/3 πr^3=0
r^3= (3v )/2π
r^3= (3 ×125000 )/2π
r^3= 59683
r= ∛59683
r = 39.1 cm
to calculate the height
h=(125000- 2/3 π〖39.1〗^2 )/(π〖39.1〗^2 )
Height = 25 cmsorry can figuare how to make the equations non linnear