the formula for the surface area of a sphere is 4πr^2 (π is pi by the way, it looks weird here), but i was wondering... what is the radius exactly? would it be wrapping a belt around a ball and cutting that in half or driving a stick through the middle to get through the other side, and taking half of that? (in other words half of the equator or half the axis?)
2007-07-30 10:19:20 · 7 answers · asked by Fundamenta- list Militant Atheist 5 in Science & Mathematics ➔ Mathematics
radius of a sphere is given by half of its axis.
length of equator will give its largest circumference, using which also can the radius be calculated (=πr^2).
so, driving a stick through the middle to get through the other side, and taking half of that will give the radius of the sphere
2007-07-30 10:31:24 · answer #1 · answered by Vipin A 3 · 0⤊ 0⤋
The radius of a sphere is the same as the radius of a circle:
it is the distance from the center of the sphere to the outside points.
So with your analogies, it would be driving a stick through the middle and taking half of that distance.
2007-07-30 10:32:00 · answer #2 · answered by Anonymous · 0⤊ 0⤋
A sphere is defined in the following way:
Pick a point in space. Pick a radius, "R". All points whose distance from the first point is equal to or less than R are part of the sphere. All points whose distance from the first point is greater than R are outside the sphere.
The surface of the sphere is simply all points whose distance from the center is equal to R. In simple terms, the radius is the distance from the very center of the sphere to the surface.
2007-07-30 10:30:50 · answer #3 · answered by lithiumdeuteride 7 · 0⤊ 0⤋
The radius is "half of the axis," as you describe it. Your "stick" measurement is giving you the diameter D of a maximal circular cross-section of the sphere, and that D = 2 r, where r is the radius.
In contrast, you "belt method" is measuring the circumference C of such a maximal circle, and C = 2π r, as it is when examining plane old, plane circles, of course. So to get r from your belt measurement C, you'd need to DIVIDE it by 2π --- nowhere near as convenient!
Live long and prosper.
2007-07-30 10:30:28 · answer #4 · answered by Dr Spock 6 · 0⤊ 0⤋
what is the radius exactly= driving a stick through the middle to get through the other side, and taking half of that? ( half the axis?)
2007-07-30 10:30:22 · answer #5 · answered by harry m 6 · 0⤊ 0⤋
radius = (diameter / 2) or
radius = sqrt(area / PI)
http://www.csgnetwork.com/circlecalc.html
2007-07-30 10:30:47 · answer #6 · answered by Dal N 4 · 0⤊ 0⤋
half the stick analogy gets u there...lol
2007-07-30 10:29:30 · answer #7 · answered by Kenneth H 3 · 0⤊ 0⤋