Radius Definition and 1000 Threads

  1. J

    Radius of circumference as function of arc lenght and height

    Homework Statement I don't know the radius of the circumference. I could only measure the arc lenght, and the height. I know the guidelines say we should not post images, but this is a geometric problem and I think it is something logic to show it with a picture. So the variables are the...
  2. W

    Radius of helical motion in a magetic field

    Homework Statement When the charge enters the magnetic feld at an angle x , how the radius can be expressed as? Homework Equations Force of charge in a magentic field = qvbsinx centripetal force = mv^2/r The Attempt at a Solution when i combined the two equations above, i got...
  3. D

    Angular velocity of an object with radius and time

    Greetings, I fell upon a certain question and it seemed that no matter what I did I was unable to solve it. I wished to know how if given a radius of 0.6m and the time for one revolution: 0.3s, to find the angular velocity in radians of the object. Consider it to be a point particle. Thanks
  4. L

    Minimum Radius for 2.4GHz RC Car Loop Experiment

    I need a general rule of thumb or simple formula to determine the minimum radiius required for an experiment. I have a 2.4GHz remote control car that reaches about 45 mph. If I begin at a certain distance from the loop at ground level, how large will that loop need to be? The car measures 19"...
  5. O

    How can the atomic radius of any atom be accurately calculated?

    hello, I was wondering how the atomic radii where calculated. I have used the formula r=\frac{a_{o}n}{z*/n*} where z* is effective nuclear charge and n* is the effective principal quantum number but it seems to give me a bit different radii compared to the ones on Wikipedia...
  6. K

    Angular Acceleration and Radius

    I am writing a lab report for an experiment where we used a rotary motion sensor with different sized disks to find angular acceleration as a string attached to a falling weight unraveled and accelerated the disk. I am having confusion with my graph results and am wondering if they are correct...
  7. D

    Radius and interval of convergence

    Homework Statement infinity ∑ (x^(n+5))/3n! Find the radius of convergence and interval of convergence n=0 Homework Equations The Attempt at a Solution I got 0 for the radius and 0 for the interval of convergence using the ratio test. This is no right. Can someone please help me? Thank you
  8. MarkFL

    MHB Radius of Sphere Inscribed in Square Pyramid: Michelle's Q&A

    Here is the question: I have posted a link there to this thread so the OP can view my work.
  9. K

    MHB Express material cost as function of radius

    Hey guys! So I am taking an algebra class at a college but I am still in high school. And I have been really struggling with it. This is one of the problems that has me quite confused: A can in the shape of a right circular cylinder is required to have a volume of 500 cubic centimeters. The...
  10. P

    About stretching a sphere by a radius of a.

    Homework Statement Copy-paste from my textbook: Let S_1 be the sphere of radius 1, centered at the origin. Let a be a number > 0. If X is a point of the sphere S_1, then aX is a point of the sphere of radius a, because ||aX|| = a||X|| = a. In this manner, we get all points of the sphere of...
  11. N

    Solving Saturn's Rings: Calculating Radius & Particle Size

    Homework Statement Hello. I have this examples about Saturn: A) Calculate the radius of the inner edge of the Cassini division, if you know that this sharp transition in the density of the rings is caused by a 2:1 orbital resonance with the moon ring particles with a moon Mimas, which around...
  12. M

    Finding the radius of a curved surface

    I have a curved surface which I know the (x,y and z) coordinates for 5 separate points on it and I was wondering how to determine the radius of this curved surface from the coordinates and then interpolate so that I can obtain points across the whole surface? Many thanks.
  13. T

    Voltage of cylinder of radius R

    εHomework Statement A very long solid cylinder of radius R = 6 cm has: -uniform volume charge density ρ = +7 µC/m3. -linear charge density λ = 7.9168E-8 C/m Outside: What is the electric field at a radial distance of 7 cm from the axis of the cylinder? Inside: What is the electric field...
  14. H

    Charge density of a disk with radius a in cylindrical coordinates

    To write the uniform charge density of a disk with radius a in cylindrical coordinates, If we do this form: \rho (x)=\frac{A\delta(z)\Theta (a-\rho)}{\rho} (A is constant that sholud be determined and \theta is step function), we get A=\frac{Q}{2\pi a} and so: \rho (x)=\frac{\frac{Q}{2\pi...
  15. G

    Rate of change of area of circle in respect to radius

    What is the Rate of change of area of circle in respect to radius when radius is 3in I know that that dA/dr is equal to the circumference of the circle But where does that come from? Also the formula for the circumference of the circle is 2(pi)r But the answer is 6 (pi)in^2/in. I understand...
  16. S

    Cyclotron - relationship between velocity and radius

    cyclotron -- relationship between velocity and radius in a cyclotron the radius of the path of electron increases.but how if the velocity of the electron is accelerated its kinetic energy should only increase but why is it's radius increasing despite the fact that it's moving to the dee with...
  17. G

    Find charge and radius of conducting spheres given voltage and electr

    The electric potential immediately outside a charged conducting sphere is 200 V, and 10.0 cm farther from the center of the sphere the potential is 150 V. Determine (a) the radius of the sphere and (b) the charge on it. The electric potential immediately outside another charged conducting sphere...
  18. R

    MHB Find arc length given chord, radius

    The solution to this question (whose answer is pi) is eluding me: The radius of a circle is 3 feet. Find the approximate length of an arc of this circle, if the length of the chord of the arc is 3 feet also.
  19. D

    Energy and radius of a shock wave

    Homework Statement A shock wave moves away from the center of the explosion, its pressure is decreasing, and its speed tends to a constant value. In the filming of a particular explosion, the following data was obtained: t(s): 0, 0.02, 0.04, 0.06 ,0.08, 0.1, 0.12, 0.14, 0.16, 0.18...
  20. H

    MHB Radius of Sphere Tangent to Two Lines

    I need help getting around this Calculus 3 problem. Any hints will be gladly appreciated: Find the radius of smallest sphere that is tangent to both the lines L1 : x=t+1 y=2t+4 z=−3t+5 L2 : x=4t−12 y=t+5 z=t+17
  21. L

    MHB What is the height of a cone's lateral surface minimum confined to a sphere?

    (2) Find the height of the cone's lateral surface minimum confined to a sphere of RADIUS R. the answer is (2 + sqrt(2)) R
  22. J

    Radius of effect of atomic interactions

    Suppose that I have an atom in one corner of a room, and I fire a photon toward the opposite corner (and assume that it is absorbed there into the wall). There is essentially zero probability that that photon will interact with the atom (either be captured, or stimulate emission, or whatever)...
  23. B

    What is the radius of a superposition

    Does superposition have a radius or a space covered distance which cuts off at a certian point based on the size or coherance of the object. I understand it is a statistical distribution like a blanket of qm possibility as to where the object or particle can collapse. But is there a cut off...
  24. T

    What Radius Produces Intensity Minimum?

    Homework Statement In the figure, sound with a 38.0 cm wavelength travels rightward from a source and through a tube that consists of a straight portion and a semicircle. Part of the sound wave travels through the semicircle and then rejoins the wave that goes directly through the straight...
  25. S

    Radius of a planet, given the density

    Hello! I'd like to thank everyone in advance for any help I receive! Homework Statement In January 2006, astronomers reported the discovery of a planet comparable in size to the Earth orbiting another star and having a mass of about 5.5 times the Earth's mass. It is believed to consist...
  26. L

    What is the Radius of Curvature at Point B on the Road?

    Homework Statement The speed of a car increases uniformly with time from 50km/hr at A to 100km/hr at B during 10 seconds. The radius of curvature of the bump at A is 40m. if the magnitude of the total acceleration of the car’s mass center is the same at B as at A, compute the radius of...
  27. K

    Centripetal acceleration and radius

    I am curious how to tell how centripetal accel. changes with radius since there are two equations I can look at a = v2/r or a=wr I read on a thread that if v is constant then use the top equation and if w is constant then use the bottom equation. Is this true? If so, can you please give...
  28. T

    Heat transfer question - Graphing temperature versus radius

    Here is the solution to the problem, all you need to look at is the diagram, the conductivity values and the graph. What I don't get is why the temperature is not continuous when the material changes. Shouldn't there be equilibrium at the boundaries between the different materials?
  29. G

    Gravity - Why do we Use Radius of Earth in Calculating Surface Gravity

    Newton showed that F=G(m1m2)/r2 When calculating the force of gravity on the surface of the Earth, why do we use the radius of the Earth for our r value? Of course, the above Newtonian equation suggests we should, but it seems rather counter-intuitive. I must admit to not having taken a...
  30. elDuderino81

    Finding Planetary Radius using density and escape velocity

    [b]1. "Calculate the radius of a planet with mean density of 3.0x10^3 m2kg-3, from which a golf ball can be thrown to infinity as a velocity of 40 ms-1" Homework Equations I've been looking at the equation of: Vesc=sqroot of 2*G*M/r and rearranging to r=2*G*M/Vesc. However, the...
  31. U

    How does the wavelength of light affect the radius of a diffraction disc?

    Homework Statement Visible light passing through a circular hole forms a diffraction disc of radius 0.1mm on a screen. If X-ray is passed through the same set up, what will happen to the radius of diffraction disc? The Attempt at a Solution I'm really clueless regarding this question. I...
  32. GeorgeDishman

    Gravitational time dilation for a spherical body of finite radius

    I am considering the gravitational time dilation at the centre of a spherical, non-rotating body (such as the Earth). The usual formula for gravitational time dilation is √(1-r_s/r) where r_s is the Schwarzschild Radius and r is the radius of the clock compared to one at infinity, however, this...
  33. ryanuser

    Is schwarzschild radius, where the whormholes could be made?

    Comment, discuss and explain please. Thanka
  34. B

    Capacitor question - Estimate the required radius of each plate

    Homework Statement Estimate the required radius of each plate. The plates are separated in air by 0.01mm and has a capacitance of 400pF. There are 4 pairs of plates. Homework Equations c= εrε0*A(n-1)/ d The Attempt at a Solution Find area. Transposing for A A = dc/εrεo A=...
  35. M

    Calculating Angular Momentum when Radius Changes for 2s

    26. A 2.0-kg block starts from rest on the positive x-axis 3.0 m from the origin and thereafter has an acceleration given by a = (4.0 m/s2)ˆi (3.0 m/s2)ˆj. At the end of 2.0 s its angular momentum about the origin is: A. 0 B. (36kg·m2/s)kˆ C. (+48kg·m2/s)kˆ D. (96kg·m2/s)kˆ E. (+96kg·m2/s)kˆ...
  36. caffeinemachine

    MHB Can 101 Discs of Radius 1/2 Cover a Rectangle That 25 Discs of Radius 1 Can?

    Hello MHB. I am having trouble with the following quesion. Let $R=\{(x,y)\in\mathbb R^2:A\leq x\leq B, C\leq y\leq D\}$ be a rectangle in $\mathbb R^2$ which can be covered (overlapping allowed) with $25$ discs of radius $1$ each. Then $R$ can be covered with $101$ rectangles of radius $1/2$...
  37. G

    Derivation of Schwarzschild radius from escape velocity

    Hi, Is it pure coincidence that if you put ##c=v_e=\sqrt{2GM/R}## in the escape velocity, you end up with the Schwarzschild radius ##R=2GM/c^2##? The derivation of the escape velocity is purely classical mechanics. It involves ##E_{kin}=mv^2/2## which is incorrect in special relativity...
  38. J

    Finding Radius & Interval of Convergence

    Homework Statement Find the radius of convergence and the interval of convergence Homework Equations A_n = Ʃ sum n =1 to infinity [((-1)^n) x^(2n+1)]/(2n+1)! The Attempt at a Solution All I thought was to use the ratio test so I did A_(n+1) /A_n = ((x^(2n+1))/(2n+1)!) (...
  39. L

    Can I integrate to find resistance of an object of increasing radius?

    Homework Statement I have to find the ratio of RB/RA where R is electrical resistance. Both objects A and B have circular cross section and length L, and are made of the same material. A has radius r0. B has radius r0/2 at the bottom and increases linearly to 2r0. Homework Equations...
  40. AakashPandita

    Angular acceleration x radius= Acceleration of center of mass ?

    For a rotating body, (angular acceleration x radius)= Acceleration of center of mass ? But a rotating body can have angular acc. even if it is not translating. what is wrong?
  41. P

    Flux that reaches a certain radius in a star

    I know the radiative flux traveling through the atmosphere of a star obeys the equation: dF/dr=-opacity*F*density If we have an isothermal atmosphere the density decreases with radius such that density is proportional to 1/r^2. If the flux entering such an atmosphere from the core of...
  42. K

    Related Rates (increasing cone radius question)

    Homework Statement I've worked through both parts of this question twice in what I assume is the correct manner, but I'm receiving an unexpected result from part B. The question is as follows: Sand is dumped such that the shape of the sandpile remains a cone with height equal to twice...
  43. Albert1

    MHB Find the radius of the small circle O_2

    find the radius of the small circle O_2:
  44. P

    Finding the speed of a block only by using the angle and Radius

    Homework Statement A small block is standing on top of a big smooth sphere. The small block is initially at rest. The block then glides down the sphere. The block is standing a little to the side for it to move down the sphere but it can be assumed that it is starting at the top. The radius...
  45. M

    Mass loss in relation to radius of a star

    One of the most popular mass loss equations of a star, developed by D. Reimers, is given by: dM/dt = -(4x10^-13) * η(L/(gR)) solar masses per year Where η is a free parameter close to unity and L, g, and R are the luminosity of the star, surface gravity of the star, and the radius of the star...
  46. X

    Radius and interval of convergence help

    I have a problem: the radius of convergence for the power series \sum(-1)^n \frac{(x-3)^n}{(n+1)} is R=1. Determine the interval of convergence. What does this mean? can anyone help me solve this please
  47. I

    Expressing the limits of integration for radius in polar coordinates

    i'm trying to integrate some some function bounded by the x-y domain of x2+y2=6y which is a circle on the x-y plane shifted upward where the outer part of the circle is 6. i'm trying to integrate a double integral.. ∫∫f(x)rdrdθ i don't know how to express my limits of integration for r...
  48. N

    Radius of convergance complex power series

    Homework Statement https://scontent-a.xx.fbcdn.net/hphotos-ash3/1390611_10201748262844961_2141774184_n.jpg I need help with 7b. Theorem 3 = termwise differentiation and theorem 4 = termwise integration.Homework Equations The Attempt at a Solution I have no idea how differentiation or...
  49. 1

    Radius of Specimen from Flexural Strength

    Homework Statement A circular specimen of glass is loaded using the three-point bending method. Compute the minimum possible radius of the specimen without fracture, given that the applied load is 4000 N the flexural strength is 65 MPa, and the separation between load points is 35mm...
  50. K

    Calculating Satellite Aperture Radius

    Homework Statement Estimate (in the order of magnitude) the size of a satellite lens (aperture radius) required to resolve a human face at the surface of the Earth if the satellite is orbiting at an altitude of 100km. Assume λ to be 600nm.Homework Equations θ = 1.22 (λ/D)The Attempt at a...
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