Circumference Definition and 111 Threads

I was wondering about how to find the circumference of an ellipse. I googled for it and found this: http://paulbourke.net/geometry/ellipsecirc/ That got me pretty amazed! I don't know high level maths, but still, can someone please explain to me why the circumference takes such a complicated...

What is the circumference of a four dimensional sphere?

Homework Statement We have an electron in 3D space in which there is also a magnetic uniform field B=Bz. At t=0, we have z=0 and $v_z=0$. We have to find the center of the circumference traveled by the electron using only x, y, v_x and v_y (coordinates and velocity of the electron at the...

My professor was showing us how to calculate the Circumference of the Earth using Eratosthenes method, as shown here. I completely understand this method. http://www.bsin.k12.nm.us/Curriculum/CAP/completed%20files/astronomy/completed%20files/eratosthenescircumf.html However he told us he had...

My professor was showing us how to calculate the Circumference of the Earth using Eratosthenes method, as shown here. I completely understand this method. http://www.bsin.k12.nm.us/Curriculum/CAP/completed%20files/astronomy/completed%20files/eratosthenescircumf.html However he told us he...

Homework Statement The circumference of a ball is 29.6 inches. Given that the radius of Earth is about 6400 km, how many balls would it take to circle around the equator with the balls touching one another?Homework Equations (d)(pi) = circumference 1 inch = 0.0254 meters 1 km = 1000 meters...

The event horizon of a Kerr black hole is often depicted as being spherical, but this seems to be a reference to the horizon as defined in Boyer-Lindquist coordinates, where horizons appear at a constant value of r. However, Thorne describes the "black hole's horizon bulg[ing] out at its...

Homework Statement We are given a function defined by x = uv, y = 1/2 (u^2-v^2)Homework Equations I derived the line element ds^2 = (u^2+v^2) dv^2 + (u^2+v^2) du^2 However I decided this was to unwieldy to derive our circumference where C = 2*{R}\oint_{-R}^{R} ds So I decided to try to...

1. When the sun was directly overhead in syene, why was it not directly overhead in Alexandria The size of Earth was first measured in Egypt by Erathosthenes about 235 BC. He calculated the circumference of Earth in the following way. He knew that the Sun is highest in the sky at noon on June...

Sometime in the afternoon or in evening i see some leaves caught in something like air current which i feel that there some thing more. The leaves (tiny fallen leaves and some dust particles) revolve around a center. It looks like the leaves have formed the circumference of the circle and they...

Homework Statement A circle is inscribed in a triangleHere is a picture Picture of circle inscribed in triangle, not necessarily to scaleWhich is larger: the circumference of the circle, or the perimeter of the triangle? Homework EquationsC=∏D (D=diameter of the circle, C=circumference of...

I have a question about a spinning spool, there is a spool spinning and is the sistance traveled by the circumference the same as the center of the circle? You can refer to the diagram attached for a question I had trouble with from a physics olympiad. The answer was (B). Thanks in advance!

Hello again, I'm finding myself stuck on what is probably a simple question, but I believe I am taking the wrong approach. The section is "Volumes with infinite integrals," and the chapter is "Improper Integrals." The question, "Use calculus to find the circumference of a circle with radius...

Here is the simple question. When I differentiate the area of a circle, I got the parameter. As the Area is the sum of Circumference. But why cannot I get the circumference of ellipse by differentiate the area with respect to the radius (I set it as the longer side). The answer I got is...

Homework Statement A very thin disk of non-conducting material initially holds a charge QO = +5 μC that decreases with time t as Q(t) = QO e-t/τ where τ = 10 seconds. If the disk has a radius of 0.10 m, what is the magnitude and direction of the magnetic field at the circumference of...

Homework Statement Find the equation of a circle if the circumference is 18∏ and contains the point (2, 8) The Attempt at a Solution I know I can find the radius by setting 18∏=2∏r. r=9. the equation of a circle is (x-h)2+(y-k)2=r2 So I have 92= (2-h)2+(8-k)2 which becomes...

Hello there, This is my first post in this forum and I am so excited! I have got this question as my homework ,but i couldn't understand what exactly been asked in this question.the question says : A right angled isosceles triangle ( with two equal sides ) is cut from each corner of a...

i am trying to figure out how to calculate the circumference of a circle in the Poincare Half Plane. I know that vertical lines are geodesics so using the arclength formula, the distance between 2 points (x_0, y_0) and (x_1, y_1) on a vertical line is ln(y_1/y_0) . Thus, if i have a circle...

all of my work so far is in the picture. I'm stuck on what i should do next.

Homework Statement By employing spherical polar coordinates show that the circumference C of a circle of radius R inscribed on a sphere S^{2} obeys the inequality C<2\piR The Attempt at a Solution I proved C=2\piR\sqrt{1-\frac{R^2}{4r^2}} So if r>R, then the equality is correct. Am I right...

Hello, First of all - I love this forum - so many interesting topics! My question is quite complicated - at least for me. My high level goal is to measure lean angle based on the difference of speeds between the front wheel of the bike vs the 'real speed' (let's just assume I have the...

Homework Statement I believe this is intended to be a proof of the formula πrl, surface area of a cone. Homework Equations A complete volume of revolution gives you a cone - the height h is the x value on a graph, the radius r is the y value. The y intercept is zero, therefore y=r/hx ...

Homework Statement Just got done reading the chapter... Want to make sure I have this right... IF Circumference = 2(pi)r Let cir = 360 deg. So that 360 deg = 2(pi)r And 180 deg = (pi)r IF r = 10 then 180 = (pi)10 Hence half of a cirlce with radius of 10 has an arc measure of...

Hey Guys, For a maths assignment, we were given this question to complete: http://nrich.maths.org/5673 I'm having an discussion with a friend of how best to approach it. Should I work out and differentiate the area or perimeter (for the circle)? If we're finding the cost of materials, then...

Hey friends! How can the set of all points on the circumference of a circle be an Infinite Set? Anyone could explain? Thanks in advance! -Saphira :)

Homework Statement Consider the ellipse given by the parametric equation x=3cos(t) y=sin(t) 0\leqt\leq2\Pi. Set up an integral that gives the circumference of the ellipse. Also find the area enclosed by the ellipse. Homework Equations \int\sqrt{1+(dy/dx)^2}dt The Attempt at a...

Homework Statement Suppose that the radius X of a circle is a random variable having the following p.d.f.: f(x)={ (1/8)(3x=1) for 0<x<2 0 otherwise Determine the p.d.f. of the area of the circle and the circumference of the circle. Homework Equations...

Hi, Can someone please tell me how to calculate circumference when two cylinders are intersects each other marked with red color such as below image? Thanks in advance Huygen http://i44.tinypic.com/b9a93q.png

Homework Statement x^2+y^2=1 Homework Equations length of curve square root (1+(dx/dy)^2)dy or square root ((dx/dt)^2 + (dy/dt)^2) dt [b]3. The Attempt at a Solution [/b I isolated y and got y= square root (1-x^2) finding dy/dx = -x/square root (1-x^2) i plugged that...

Homework Statement find the cumference of the loop 9x^2=4y^3 from (0,0) to (2/3, 1) Homework Equations length of curve square root (1+(dx/dy)^2)dy or square root ((dx/dt)^2 + (dy/dt)^2) dt The Attempt at a Solution i said x=9t/4 and y= (9t^(2/3))/4 then i found that...

A student runs at a speed of 8.50 m/s on a circular track. If she accelerates a 1.03 m/s2, what is the circumference of the track? 8.5m/s*1.03m/s?

Why do we take pi as the ratio of the circumference to the diameter, and not diameter to the circumference? Is it because circumference is always bigger than the diameter, so that it will be easy to work with the ratio? Or is it something fixed by those who discovered it and we can't change it?

Spinning "tornado" wheel - circumference and radius Another quote from my current lecture "elgant universe": Page 63, 3rd Paragraph This doesn't make much sense to me. While I can comprehend that the ruler must be shortened as it's layed out tagentially to the circumference, as it's moving...

Hello. This is my first post. I just started physics this year, and I forgot how to do some simple trigonometry, but I'm not quite sure where to look. 1. My question is: If I know the circumference of the Earth at the Equator is about 2.49 x 10 to the Fourth, How do I find the...

Hi all, Hope you can help. How can I get the circumference of a specific point on a ball, more to the point in this example, the ball is in question is planet earth. Using the polar circumerence I have got the polar diameter and radius (r) (that's the easy bit). Now, what I figured is that...

Imagine a strange event: I've asked this question so many times, but have never received a clear cut answer: Let's say that you had a pole, one that you were holding up vertically, that had the length of the circumference of the Earth (24,901.55 miles). Let's just pretend that, although the...

What's the circumference of a circle of radius r, on a sphere of radius R?

I don't feel the formatting is right for this question because it's not a problem, it's just algebra I'm not getting. A(r)= (pi)(r)^2 C= 2(pi)r r= C/(2pi) therefore, A(c)= pi[c/(2pi)]^2 but I don't understand how this is supposed to equal A(c)= C^2/4pi my attempt: A(c)=...

I'm looking to find the proper formulas and/or Matlab code to localize a point within a circle given 2 points on the circumference. The points will be acquired by an image panel that rotates about a fixed axis. The hitch is that I am using flat image panels that are tangent to the circle at...

can we prove the ratio of circumference to diameter is same for all circles & is equal to pi?

Does the electromagnetic or acoustic resonant frequency of a hallow spherical object ever equal the circumference of that object? If not what are the formulas to calculate this? Thanks in advance.

Homework Statement http://urlcut.com/katrolafbeelding.gif What is the accelaration of a point on the circumference of the disk? Homework Equations \tau = F.R = I.\alpha I = M.R²/2 a = R.\alpha F(z) = m.g The Attempt at a Solution The mass exerts a force F(z) = m.g on...

Although a circumference would be finite as it encloses a finite space, if you said that the diameter was infinite (presuming you can say that) would this then make the circumference is infinite? Another was to look at it, is if you take a circle of finite size and then keep enlarging it to...

Homework Statement Given is a parallelogram which has diagonals of the length 7 (e) and 9 units (f). How big is its circumference? The sides are a,b,c,d; a being the bottom side, rest is anti-clockwise... alpha is the angle of a etc... Homework Equations no are given, i guess...

Homework Statement i know Circumference is C = pi . d if i have a wheel that need to be rotate in given time, how much centimeter i need to rotate in 1 sec?.. Homework Equations if i have this : Diameter = 5cm Circumference = 15.7cm Given time = 60sec The Attempt at a Solution and i got the...

I've found a new way for finding the circumference of a circle by using a visual perspective ,an angle of 18 degrees, and law of sines, its formula is: R is the radius of the circle r is the new radius C is the Circumference h=17.7062683767 t=3.23606808139 (R/h)= r (r/t)*360=C with...

I read the entry about the Ehrenfest rotating disk paradox on Wikipedia, but the entry does not actually answer my question about what happens to the circumference of the disk in the "resolution of the paradox" section. All I want to know is what happens to the circumference of the rotating...

Homework Statement Find the angular velocity and period of oscillation of a solid disc of mass m and radius R about a point on it’s surface. Homework Equations ? The Attempt at a Solution This is really giving me trouble because it seems like a SHO problem mixed with a rotational motion...

Suppose I know city A is located at latitude 21 degrees exactly and city y is located at latitude 24 degrees exactly. I know the distance between the two cities is 400 kilometers. I want to find the circumference of the Earth approximately How do I do this? My feeling is that we...

I was just trying to get the actual range of circumferences for the Earth depending on which way you measure (just based on math, of coure, I know the actual circumference could be considered nearly infinite depending on the length of your ruler). Wikipedia has a very nice table of stats...