Sphere Definition and 1000 Threads

Homework Statement A 'hammer' thrown in athletics consists of a metal sphere, mass 7.26 kg, with a wire handle attached, the mass of which can be neglected. In a certain attempt it is thrown with an initial velocity which makes an angle of 45 degrees with the horizontal and its flight takes 4...

If I were to drop a sphere down a tube of fluid. What are the effects of the wall of the tube on the sphere? Assuming the sphere has an extremely low Reynolds number of less than 1. Is it right to say that the ratio of the radius of the tube and the radius of the sphere has an effect on the...

Hope I am on the right forum (and that my question makes some sense-so here goes. Imagine we are a race of people living on a sphere (not hard because we are) However , rather than buying into the idea that lines are ideally straight we are and have always been well aware of how "parallel...

My first homework for electrostatics course I'm taking is to find the vector of electric field of a completely hollow sphere (radius r, surface charge density σ in a point A, by integrating the electric field through the whole sphere. I already figured out the electric field of a ring in a point...

Hi everyone, I am trying to find out the Moment of Inertia of a sphere which is all known to be 2/5(m)(r^2) I calculate this in 2 ways. One by triple integration and one by disk method. From the textbooks, moment of inertia should be in the form, dI = (r^2) dm, However, the textbook, University...

Homework Statement 1) Two solid conducting spheres have radius r1 = 3 cm and r2 = 42 cm. The two spheres are connected by a thin conducting wire. Assume: - the wire is very long and thin, with negligible surface area, so it does not affect the capacitance of the system. - the switch is...

Homework Statement What is the area of a triangle on Earth that goes from the North Pole down to the equator, through the prime meridian, across the equator to 30 degrees east longitude, then back up to the equator? The radius of the Earth is about 6378 km. Homework Equations alpha + beta +...

Homework Statement A solid insulating sphere of radius a = 4.3 cm is fixed at the origin of a co-ordinate system as shown. The sphere is uniformly charged with a charge density ρ = -421 μC/m3. Concentric with the sphere is an uncharged spherical conducting shell of inner radius b = 14.6 cm, and...

Homework Statement Does the line through the points (−1, −1, −2) and (1, 2, 1) intersect the unit sphere? If so, find the point(s) of intersection. Homework EquationsThe Attempt at a Solution do i also use r = r0 + vt but instead , use equation of sphere this time? so it would be: v=<2,3,3>...

Homework Statement A point charge of +5.00 μC is located on the x-axis at x= 5.00 m , next to a spherical surface of radius x= 4.00 m centered at the origin. [/B] According to Gauss's law, the net flux through the sphere is zero because it contains no charge. Yet the field due to the external...

Hi, Given a 3D object in R3 space can we represent it using three basic primitive shapes like Sphere, Cone and Cylinder? Would this claim be valid?

Homework Statement Compute \int_S \vec{F} \cdot d\vec{S} \vec{F} = (xz, yz, z^3/a) S: Sphere of radius a centered at the origin.Homework Equations x = a \sin(\theta) \cos(\varphi) y = a \sin(\theta) \sin(\varphi) z = a \cos(\theta) Phi : 0->2 pi, Theta : 0->pi/2 . The Attempt at a...

Homework Statement [/B] A sphere of radius $1m$ and mass $25 Kg$ is put on another sphere of radius $5 m$ and $7 Kg$ which is placed on a smooth ground. Now the upper sphere is pushed very slightly from it's equilibrium position and it begins to fall. Now when the line joining the centre of...

Homework Statement Perform potential energy W of a non-uniform density sphere by density d=d(r) and o(r)=dW/dm. Homework Equations The answer is W=1/2.integral(from 0 to R)(4x3.14xd(r)xo(r)xr^2xdr). The Attempt at a Solution I have solved this by this way: o(r)=-GM(r)/r...

Homework Statement Given a spherical shell of radius R and the surface charge density ( being the angle from the top of the sphere and being a constant) find the electric potential and the electric field inside and outside the sphere. Check that both the potential is continuous inside and...

Write the equation of the sphere with radius 7 and center on the positive z-axis, if the sphere is tangent to the plane z=0. I know this is an easy problem if i understood the terminology better. The equation of a sphere (x-h)^2 +(y-k)^2 +(z-l)^2 = 49. I know that the plane z is the set...

This question is mostly about group theory but I would like to understand it in the context of qubits rotating in a Bloch Sphere. What my understanding of things are right now: In the rotation Lie Group ##SO(3)##, we have three free parameters (##\frac{n(n-1)}{2}##), and this is also why we end...

What is the basic matrix form for a uniform (unit) sphere centered at the origin? Given a vector that specifies the radii (1,1,1) == (r1,r2,r3), I would like the matrix that implies no rotation (is it [[1,0,0],[0,1,0],[0,0,1]]?) and covers the rest of the necessary parameters. I am testing...

Homework Statement Here is the question: "In the fall of 2002, a group of scientists at Los Alamos National Laboratory determined that the critical mass of neptunium-237 is about 60 kg. The critical mass of a fissionable material is the minimum amount that must be brought together to start a...

Hello all, I am doing homework and have come upon this question: A cylindrical hole is drilled all the way through the center of a sphere (as shown in the figure below). Show that the volume of the remaining solid depends only on the length L of the hole, not on the size of the sphere. Figure...

Hi, this is my modified post since I've been told that I have to use certain format. I hope this is good now. Homework Statement Copper (conductor) sphere of radious R with an spheric bubble inside placed at distance c from the center, with radius b. The metalic sphere has charge Q.Homework...

A very basic question: does such a cone, where the broad end is not cut flat but follows the surface of the sphere whose radius is the length of the cone's side, and is centred at the cone's point, have a name?

Homework Statement A hollow spherical shell (B) with inner radius R2 and esternal radius R3 is negatively charged with Q. A spherical conducter (A) with radius R1 is placed within the the shell. A is charged with Q. The centers of both shells coincide. Then a negative point charge q is placed...

I almost understand how the inverse square law is derived from the area of sphere equation, 4πr2, but I'm not quite clear on what happens to the 4π. I found one equation that seemed to say that the intensity is equal to the area of the sphere of the source point times the amount of whatever...

Homework Statement A particle is placed on top of a smooth (frictionless) sphere of radius R. If the particle is slightly disturbed, at what point will it leave the sphere? Homework Equations Same as first question, just F = ma = ΣF_i The Attempt at a Solution Similarly, we want to know when...

If mass curves spacetime in its vicinity, then consider the following case- Take a heavy hollow lead sphere which has 2 smaller lead balls placed in it. The Outer Sphere will curve spacetime around itself and thus will have its own gravity, but what about the 2 balls placed in it? The spacetime...

Homework Statement Fans at a stadium produce sound that is heard 1km away, the intensity level is 60 dB. How much acoustic power is generated by the fans? Homework Equations B = 10 log (I÷I_0) P=I*A The Attempt at a Solution I= 10^-12*6^10= 10^-6W/m^2 P= 10^-6*4pi*1000^2 =12.56W However...

Homework Statement A uniformly magnetized sphere of radius R has a magnetization ##\vec M=M_0\hat z##. Calculate the force between the hemispheres whose contact surface is the zx plane. Indicate the direction of the force. Homework Equations Hints: ##\vec B_{\text{int}}=\frac{2}{3}\mu _0 M_0...

Another problem that yet I haven't managed to solve, finding the electric field due to a charged sphere of radius R using integration Homework Equations Continuous charged distribution $$|\vec E| = \frac{1}{4\pi\epsilon_0}\displaystyle \int\frac{\rho (r') dV}{r'^2}$$ The Attempt at a Solution...

What's the line integral of sphere? Is it possible to get the line integral in three dimensions? What kind of line are we integrating?

Homework Statement I got no credit in an exam for the following exercise and I've been told what's wrong but even then I am unable to solve it correctly. A conducting sphere with radius R moves with constant velocity ##\vec v =v \hat x## (v <<c) inside a constant magnetic field ##\vec B =B \hat...

It is usually said that molecules are spherical in shape, that is what we learn from our textbooks. May be what they are saying is true but only in the case of a monatomic molecule. If one considers a diatomic molecule there are two atoms that means two spheres and if it is polyatomic there is...

Homework Statement There is a cylindrical container that has a small hole of radius ##a ( < R)## at the bottom. A sphere of radius ##R## and density ##\rho_{s} > \rho_{w}## is placed in the cylinder such that it completely covers the hole (a part of it sticks out as in attached figure). The...

Homework Statement Consider a non-conducting sphere of radius 'R' and charge 'Q' is enclosed by spherical shell of radius '5R' and charge '4Q'. If inner sphere is expanded to radius '3R'.Then amount of work done by the field in this process is Homework Equations W=ε0/2∫E2dτ The Attempt at a...

Homework Statement I am preparing a report on black holes and I recently learned about a phenomenon I was previously unaware of: the photon sphere of a black hole. While reading an article on said occurrence (I have now confirmed this on multiple sources) the photon sphere which is the minimum...

Homework Statement The smooth homogeneous sphere rests in the 132° groove and bears against the end plate, which is normal to the direction of the groove. Determine the angle θ, measured from the horizontal, for which the reaction on each side of the groove equals the force supported by the end...

I'm not sure if this is the right forum - please move the thread, if not - but, here goes... I have a collection of 3d coordinates, each with a radius of varying amounts. Each of the coordinates is to be linked to each of the others, unless a third coordinate - with its radius - blocks the...

Homework Statement Flat space-time in polar coordinate is considered. The line element is ds2= -dt2+dr2+r2(dθ2+sin2θdΦ2) The actual answers are given below, but I can't come up to them. Need urgent help. Homework Equations dA = √g11g22 dx1 dx2 dV = √g11g22g33 dx1 dx2dx3 The Attempt at a...

Homework Statement Find the electric field of a sphere of radius R and charge Q outside sphere. Use only a Coulomb integral to do this. Homework Equations I know that I have to use a triple integral to find the E-field. I am just unsure of my whole setup really. The Attempt at a Solution...

There is a nice problem in Taylor: Classical Mechanics of a puck sliding without friction down a sphere in a uniform gravitational field (problem 4.8). The question there was at which height the puck takes off from the sphere, which is not hard to solve using conservation of energy. This...

How big would a sphere of U238 have to be to reach 1g at its surface?

Hello, I am having an issue understanding something about the RCS of a sphere. The radar cross section of a sphere in the back-scattered, mono-static direction is simply equal to the spheres cross sectional area, for wavelengths much less than the circumference. In the following link...

Homework Statement My teacher said that static friction can't slow down a sphere, when I during his office hours, and he gave he said that they don't do work on a rolling sphere... instead rolling friction is what slows down a sphere. Can someone explain to me how rolling friction works and...

How to calculate some general area on a sphere for simplicity the unit sphere. Let's say I have a ball and I draw a ring on it. What is its area? I guess I need some initial point (some coordinate). Let's take a spherical coordinates with r=1. Element of area is \sin(\theta) d \theta d \phi ...

Homework Statement If a point charge is inside a Gaussian sphere but is off center, why is its electric field still Qenc/(e0*4*pi*r^2)?Homework Equations surface integral of E*da=Qenc/e0The Attempt at a Solution If we draw cones out from the charge. the 2 surfaces from the cones' intersection...

I'm trying to find the resulting location of a point on a sphere in spherical coordinates or Cartesian. Based on velocities from the perspective of an object on the sphere. So given the: location on the sphere (in spherical or Cartesian) zy - plane rotation of the point up direction of the...

A spherical shell has an outside radius of 2.75 cm and an inside radius of a. The shell wall has uniform thickness and is made of a material with density 4.59 g/cm3. The space inside the shell is filled with a liquid having a density of 1.00 g/cm3. (a) Find the mass m of the sphere, including...

Homework Statement Homework EquationsThe Attempt at a Solution Doing a vertical force balance 2Fcosθ=mg ,where m is the mass of water . Not sure how to proceed . What role does the pin hole at the top play ? I would be grateful if somebody could help me with the problem.

Find the volume laying inside x^2 + y^2 + z^2 =2z and inside z^2 = x^2 + y^2. This is a problem my professor made, so I have no way of checking my answer. What I did first was completed the square for the sphere and got x^2 + y^2 + (z-1)^2 = 1, which is a sphere of radius one shifted above the...

Homework Statement A solid sphere of mass M and radius a is released at vertical height y=R and rolls down a circular bowl without slipping, find an expression for the velocity of the sphere's center of mass at the bottom of the bowl. 2. Homework Equations ##I=I_c+Md^2## I=\frac {2} {5}...