Question about the minimum area

  • Thread starter Thread starter Lord Dark
  • Start date Start date
  • Tags Tags
    Area Minimum
Lord Dark
Messages
120
Reaction score
0

Homework Statement


hi guys, how are you all,,
my friend had a quiz and he told me about this question :
container has a square base and the volume of it V= 1000 , find the minimum area of the surface that the container can have ...


Homework Equations


A=x^2 , V=x^2 * h


The Attempt at a Solution


i started by saying: 1000=x^2 * h then i can get h =1000/x^2 and A=x^2 then i differentiate 0=2x*h+x^2*h` ... i get at the end (2000/x)-(2000/x)=0 and this doesn't make any sense ,,i tried another way ,, i assumed it should be a cube for the minimum area so i get 6x^2=1000 then i get (x=13) is the answer right?? ,, is the question even right ?? anyone knows how it should be at least ??
 
Last edited:
Physics news on Phys.org
By minimum area, do you mean the sum of the area of the six surfaces? Are there six, is the top included?
Often these questions are asked to minimise material for packaging to hold a certain volume which I'd say this question is about. Not sure though...
 
i really don't know ,, he didn't remember ,, although, if it was the minimum area of the surface of the container ,, it should be cube right ?? so can i apply this equation ?
(6x^2=1000) ??
 
i think i got it ,, can anyone check my answer now ,,

1000=x^2*y , y=1000/x^2 , surface area = 2x^2+4x*(1000/x^2) then differentiate i get 4x-(4000/x^2)=0 then i get x=10 and y=10 so it's cube alright :D
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top