Area of a sphere

Discussion in 'Physics & Math' started by theoneiuse, Mar 25, 2010.

  1. theoneiuse Theoneiuse Registered Senior Member

    Messages:
    299
    Area of a sphere = circumference^2/pi
    now what is another formula for for volume of a circle
     
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  3. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Still posting nonsense?
     
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  5. Pinwheel Banned Banned

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    2,424
    Is the answer 42?
     
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  7. S.A.M. uniquely dreadful Valued Senior Member

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    72,825
    circle or sphere?

    circle is 2D and has no volume, volume of a sphere is 4/3 *22/7 *r[sup]3[/sup]
     
  8. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

    Messages:
    8,967
    This is wrong.

    The surface area of a sphere is

    \(A = 4 \pi r^2\)

    A circle is technically 1 dimensional, and \(\pi \neq \frac{22}{7}\)(!)
     
  9. theoneiuse Theoneiuse Registered Senior Member

    Messages:
    299
    Mayby I wasn't clear
    the circumference squared of a sphere divided by pi
    is equall to the surface area of that sphere do for youself
    then tell me am wrong again
    what I wanted for volume was another equation
    another route to the same destination
     
  10. kurros Registered Senior Member

    Messages:
    793
    Ok the first part is fine, but what are you asking about volumes of circles? It was already pointed out circles have no volume. Are you wanting something relating the volume of a sphere directly to some property of a related circle? There are lots of kind of arbitrary formulae one can come up with, like it is the circumference of a great circle cubed divided by 6 pi squared:
    \(V=\frac{(2\pi r)^3}{6\pi^2}\)
    What's the point though?
     
  11. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

    Messages:
    19,252
    So what?
    Like Ben wrote: 4.pi.r[sup]2[/sup].
    All you've done with your "formula" is re-hashed it.
    Since circumference is pi.d and d = 2.r it's exactly the same thing.
    (pi.2.r)[sup]2[/sup]/pi = pi[sup]2[/sup].4.r[sup]2[/sup]/pi = 4.pi.r[sup]2[/sup].
    How does it make it it any different?
    And why would you do it that way since you're introducing an intermediate step?
     
  12. theoneiuse Theoneiuse Registered Senior Member

    Messages:
    299
    I have no point but how important is acuracy
    what situations would you think acuracy
    would be more important how do you prove
    what procesess give you the best results
     
  13. oozish Banned Banned

    Messages:
    66
    Area of a sphere = 4 * pi * r ^2

    but what is the rate of Area of a sphere in respect to time? Lets say a sphere expands at an accelerating rate, the further the time the faster the expansion rate, the rate is close to exponential, what would the rate of expansion of surface area of a sphere be with respect to time than? Initial time = 0 at which surface area = 1*10^-22, what would the surface area of a sphere be at time = 1.3*10^26 ?
     
  14. kurros Registered Senior Member

    Messages:
    793
    How is one formula more accurate than another? If they are equal they are equal, no possible inaccuracies, it is a consequence of logic. Perhaps one may offer different insights to another, but that has nothing to do with accuracy.
     
  15. theoneiuse Theoneiuse Registered Senior Member

    Messages:
    299
    I did not say Ben was wrong
    I made an attempt to communicate my point of view
    with more clarification than the previous unclear post
    this is really about what are subjective opinions on the
    value of acuracy in different situations
     
  16. oozish Banned Banned

    Messages:
    66
    C=2*pi*r = d * pi, S.S.A=4*pi*r^2

    Surface Area of a Sphere = 2*C*r = C * d = Circumference * diameter = Circumference * Circumference * 1/pi = Circumference^2/pi

    Meanwhile Area of a Sphere would include the interior area of that sphere as well so:
    Area of a Sphere = 2*C^2/pi (that is if the wall of the sphere was infinitely thin)

    Now Area of a Ball (which by definition includes its insides) is equal to Surface Area of a Sphere.
     
    Last edited: Mar 25, 2010
  17. oozish Banned Banned

    Messages:
    66
    you neglected to mention that your formula is Surface Area of a Sphere only...meanwhile area of sphere also includes the area of its insides. So your equation is incorrect as:

    Area of Sphere = Surface Area of a Sphere + Interior Area of Sphere = 2 * (Surface Area of a Sphere)

    in a condition where the sphere's wall is infinitely thin.

    What most people think of a sphere is actually in mathematics defined as a Ball. A Ball includes its own insides and thus: Area of a Ball = your equation.

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  18. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

    Messages:
    19,252
    What do you mean "accuracy"?
    There is no difference whatsoever in the calculation, all you've done is restate it in a different form.
    And by doing so you have made it harder (i.e. more complicated) to use since you've added an intermediate step - that of calculating the circumference.
     
  19. kurros Registered Senior Member

    Messages:
    793
    A (2-)sphere is just a 2D surface, double counting its area is a weird thing to do. A (3-)ball is a 3D object, which has a (2-)sphere as its boundary, so if we were talking about a ball perhaps it would be more important to specify "surface" as the area we mean.

    But who cares, I think it was clear enough what everyone (except theoneiuse) was talking about. I still don't see the point of any of it.
     
  20. theoneiuse Theoneiuse Registered Senior Member

    Messages:
    299
    If you donot know the exact quanty for pi
    then how can you know the full comprehension
    of the product circumference how do you know for sure that
    illusive polygon has the abilty to even capture
    the true essence of a circle what if the polygon was an
    infinite contradiction used to compare a natural truth
    and now the ratio of c/d will always be irrational
    under these circumstances thus all calculations will be
    inacurate
     
  21. kurros Registered Senior Member

    Messages:
    793
    Oh, back to that then. Well, I'm out.
     
  22. James R Just this guy, you know? Staff Member

    Messages:
    39,397
    No problem, since we do know it. Pi can be calculated to whatever accuracy you desire.

    Hint: try inserting full stops (periods) between sentences. And try question marks for questions.

    What's the "full comprehension of the product circumference"? Please explain.

    A circle is not a polygon, so this is irrelevant.

    What if your underpants turned blue and dropped off?

    You mean the ratio of the circumference of a circle to its diameter is an irrational number? Yes it is. You're correct.

    All spelings will be inacurate too.
     
  23. theoneiuse Theoneiuse Registered Senior Member

    Messages:
    299
    This is important for a fluid processing of infinite variables of info
    where a small inacuracy can tranform into something completey
    useless as the final product as comprehension becomes
    more relevent acuracy must also become more
    precise this will minimize probabilty the grand ascension
    is to illiminate it all together back to the acient precepts
    like is was before
     
    Last edited: Mar 26, 2010

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