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Volume of largest cylinder

  • Thread starter Amith2006
  • Start date
  • #1
427
2

Homework Statement


What is the volume of the largest cylinder that can be cut out of a cuboidal log of
wood of dimensions 30*20*10 inches?

Homework Equations


volume of cuboid = length*breadth*height
volume of cylinder= *[radius]²*height


The Attempt at a Solution



Radius of largest cylinder=5 inches
height of largest cylinder=30 inches
volume of largest cylinder=750 inch³
But book answer is 1000.

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
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Hi Amith2006! :smile:
volume of cylinder= *[radius]²*height
Yes, the radius is squared but the height is on its own.

So don't you you want the radius to be as large as possible?

ooh … gotta go now … Doctor Who starting on telly! :biggrin:
 
  • #3
427
2
Hi Amith2006! :smile:


Yes, the radius is squared but the height is on its own.

So don't you you want the radius to be as large as possible?

ooh  gotta go now  Doctor Who starting on telly! :biggrin:

so doed it seem ok?
 
  • #4
tiny-tim
Science Advisor
Homework Helper
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so does it seem ok?
No!

You want the radius to be as large as possible,

but you've made it the smallest possible (5).

Try again, and see the difference! :smile:
 
  • #5
427
2
You want the radius to be as large as possible,

but you've made it the smallest possible (5).

:smile:
The problem that i face is that i cant cut out a circle of diameter 20 inches because the height is only 10 inches. i can only do so by making the Cross Section oval.
 
  • #6
tiny-tim
Science Advisor
Homework Helper
25,832
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The problem that i face is that i cant cut out a circle of diameter 20 inches because the height is only 10 inches. i can only do so by making the Cross Section oval.
No … draw a diagram … 6 bricks in two layers of 3.

One side is 2 bricks x 3 bricks.

Draw the circle on that side! :smile:

(btw, what happened to π in the formula?)
 
  • #7
427
2

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