Radius Definition and 1000 Threads

Homework Statement http://img585.imageshack.us/img585/613/labnotebookq.gif Uploaded with ImageShack.us A Test tube filled with water i being spun around in an ultracentrifuge with constant angular velocity, w (w = omega). The test tube i slying along a radius and revolving in a horizontal...

Homework Statement Carousel is spinning when w = 1.4rad / s. on the carousel there is a given body. Static friction between the carousel with the body is 0.2 What is the radius that you can put the body on the carousel that the body won't slip? Homework Equations The...

Homework Statement A circular garden is surrounded by fencing costing $5 per meter. If the total cost of the fencing is $100, find: a)the radius of the garden b)the area of the garden Homework Equations The Attempt at a Solution all I know is that it would make sense if...

Homework Statement A bus passenger has her laptop sitting on the flat seat beside her as the bus, traveling at 10.0 m/s, goes around a turn with a radius of 25.0 m. What minimum coefficient of static friction is necessary to keep the laptop from sliding? Given: V = 10 m/s r = 25.0 m...

Homework Statement A water wheel rotates a generator producing power from vertically flowing water onto its blades. Height of water is 100m above blades. init vert velocity is 0. I have calc velocity at hitting wheel as 44.3m/s calc the mass of water hitting the wheel per second to create...

What happens to the Schwarzschild metric for an isolated non-rotating body when the horizon radius is inside the body? As I remember from classical physics all of the gravitational pull on an object inside a shell cancels out so it would seem that the horizon radius can not include any mass...

Homework Statement why is the mean square radius of a sphere given as <r2> = 3/5 R2 The Attempt at a Solution i saw this thread https://www.physicsforums.com/showthread.php?t=293397 but i don't understand the helper (malawi_glenn)'s post he put in a p(r), but what is that...

Homework Statement A dentist uses a spherical mirror to examine a tooth. The tooth is 1.13 cm in front of the mirror, and the image is formed 10.8 cm behind the mirror. Determine the mirror's radius of curvature. Homework Equations 1/p+1/q=1/f f=R/2 The Attempt at a Solution...

Hey everyone, I am not physics major and I haven't had a physics class in sometime, but for my senior project I made a spinning LED display. The original design we had was flat and had an array of leds that blinked on and off fast while the motor spun. However, when it started to spin...

I need to calculate the radius of gyration for a generic, convex polygon, where the density is constant, the axis of rotation is the centroid (which is known), and the positions of the vertices are known. Does such an equation exist?

Homework Statement A particle on a string at radius r=0.22m is moving in a (horizontal) circle with angular speed \omega =0.55 rad/s. The string is shortened to 0.15m. Show that the new angular speed is 1.18rad/s Homework Equations v = r\omega a = \omega^{2}r a = r\alpha...

Homework Statement A 5.6 MeV (kinetic energy) proton enters a 0.18 T field, in a plane perpendicular to the field. What is the radius of its path? Homework Equations kinetic energy: KE = 1/2 mv^2 velocity: v = sqrt(2KE / m) radius: r = mV/qB The Attempt at a Solution KE = 5.6...

Homework Statement If a satellite in orbit changes it's orbiting radius to 4 times its initial one, how does it's velocity change? I get different answers by using Newton's Law of gravitation and conservation of angular momentum. Homework Equations F = \frac{G M m}{R^2} a_c =...

Homework Statement A rocket is in an elliptical orbit around the earth; the radius varies between 1.12 Rearth and 1.24 Rearth. To put the rocket into an escape orbit, its engine is fired briefly in the direction tangent to the orbit when the rocket is at perigee, changing the rocket's velocity...

Homework Statement This is not so much an entire problem I need help with but just a part. It is a power series where after you do the ratio test, you end up with |4x^(2)| < 1, so |x^(2)| < 1/4. Since the radius of convergence is |x-a| < R, I end up with -1/4 < x^(2) < 1/4, but because...

There's something bothering me about the event horizons of black holes. The Schwarzschild radius (as I see it) is basically the distance from a center of mass at which the escape velocity is the speed of light. The way escape velocity is defined though is the speed a body must have to "reach...

Homework Statement a metal sphere of radius 0.39 m carries a charge 0.55 μC. Equipotential surfaces are to be drawn for 100-V intervals outside of the sphere. Determine the radius of the first, tenth and 100th equipotential from the surface. Homework Equations V = kQ / r Volt =...

Homework Statement What is the radius of gyration (in meters) for the steel flywheel shown? The width of its rim, L, is as given below. The density of steel is 7500 kg/m3. The outside diameter (OD)for the wheel is 2000 mm, and the inside diameter (ID) is 1840 mm as shown in the figure. The...

Homework Statement This is just a general question. When using Kepler's second law, which radius am I supposed to use to sub into r? Is it the radius of the object (ex. Earth's is 6.38e6 m) or the radius of orbit (ex. Earth's is 1.49e11 m)?Homework Equations C = (GM)/(4pi^2) = (r^3)/(T^2)The...

Homework Statement Find the Summation Notation and Radius of Convergence of this series. 5, x, 10, x, ... The Attempt at a Solution I don't know how did they come up with that equation.. But the summation seems right.. Can anyone tell me how did they arrive with that equation? I've tried...

Homework Statement I have a graph with the radius on the x-axis and Fc on the y axis. I had to then calculate the slope of this linear relationship. I did that, and I got 0.17. The problem is that I don't know what this represents. mass? acceleration?? Homework Equations Fc = m4π^2rf^2...

Physics puzzle: A 1" radius 7 billion K temp. ball is activated inside Jupiter... Physics puzzle: A 1" radius, 7 billion K temp. fireball is activated inside Jupiter...from an artificially induced fission reaction of .04kt. It is activated deep enough into Jupiter to be under 40,000,000...

Homework Statement Consider a simple model for the interior of the Earth: there is a spherical iron core with constant mass density ρ0 and radius a; outside the core is "rock" with constant density ρ1. Use these values for the densities: ρ0= 8.90×103 kg/m3 and ρ1= 3.80×103 kg/m3. The radius...

Is Schwarzschild radius trying to state the gravitational field on the event horizon of a black hole? If not, what is it trying to state? Can you give me a example using his formula to figure out the gravitational force of a black hole in the event horizon? Do you have any links I can...

I have a question, and I hope I can word it correctly. Say I have a round pipe of length 5 feet (actually, the length is irrelevant). I want to bend it at a certain radius in the horizontal direction, and also a certain radius in the vertical direction. Let's say I bend it at 20' horizontal...

Homework Statement A satellite is in orbit just above the surface of a spherical planet which has the same radius as Earth and the same acceleration of free fall at it's surface. Calculate: i) Speed ii) Time for 1 complete orbit. Radius of Earth = 6400km or 6400000m and accel. of free...

can anyone say why the derivation works? my teacher went through it in class and sort of said "don't question it" (which i hate) but it's still annoying me now even though it's a few weeks since i finished college. KE = GPE 0.5mv² = GMm/r r=2GM/v² and then if the escape velocity is the...

I have problem to see clearly the case of rotation of a body about a point with decreasing radius.this can be viewed as a body being rotated about a point with the help of a thread which passes through a hole in a disc and the thread is being pulled to apply a tension and gradually to decrease...

Homework Statement The radius r of a wire of length L increases according to r = a * exp(bx^2), x is the distance from one end to the other end of the wire. What is the resistance of the wire?Homework Equations R =\frac{L * \rho}{A}The Attempt at a Solution dR =\frac{dx * \rho}{A} A(r) = \pi *...

Im new to these forums and I'm looking forward to becoming a regular contributor. I'm attempting to prepare for physics in the fall and I have a textbook problem that i understand the process of solving but not understand the concept. Heres the question: What mass of a material w/ density p...

Are there any known metrics in which black holes do not have the Schwarzschild radius? Specifically, I'm interested in whether it's possible for a black hole to have an event horizon which is not of the form: constant * mass.

Frictionless, horizontal table...radius and speed...? The 0.20 kg puck on a frictionless, horizontal table is connected by a string through a hole in the table to a hanging 1.20 kg block. With what speed must the puck rotate in a cicle of radius 0.50 m if the block is to remain hanging at rest?

Does anyone know how to determine the leading-edge radius of an airfoil using just the x y coordinates.

A cart slides down a frictionless inclined track to a circular loop of radius R = 13 m. In order for the cart to negotiate the loop safely, the normal force acting on the cart at the top of the loop, due to the track, must be at least equal to the cart's weight. (Note: This is different from the...

In the Schwarzschild spacetime setting we have a vacuum solution of the Einstein field equations, that is an idealized universe without any matter at the geodesics that are solutions of the equations. This spacetime has however a curvature in both the temporal and spatial component that comes...

How do I go about finding the radius of the circle, I seem to be stumped on this question? *dimensions in attachment are not to scale, just a rough sketch.

I understand that the holographic principle applies to black holes and states that they are objects of maximum information/entropy. It states further that this information/entropy is bounded by the black hole's area rather than its volume. Apparently the holographic principle might apply to...

Homework Statement Determine the polar moment of inertia and the polar radius of gyration of the shaded area shown with respect to point P. http://imgur.com/8Kc1S Homework Equations Jp = Ix + Iy Ix = &int y^2dA Iy = &int X^2dA The Attempt at a Solution A = 2(a/2)(a) +...

Homework Statement Find a differential equation whose solution is a family of circles with centers in the xy-plane and of variable radii. Hint: Write the equation of the family as x^2+y^2-2ax-2by+2c=0 Homework Equations The previous questions asks to find a differential equation whose...

Homework Statement I need to calculate the radius of curvature of a bimetallic strip when the two strips are subjected to different temperatures. in the problem, the two metals themselves are in different temperatures. One at 180°C, other at 160°C. Anyone with good solid mechanics knowledge...

I am on my second year of study for a bachelor of medical and radiation physics and one of my friends who is studying mechanical engineering ran this question by me, I haven't really had time to go into it in any detail, i thought some of you guys might like to give it a crack: You set out to...

Hi all, these questions have nagged me for years and I have never found a text or a paper that even addresses them. Regarding photon "radius", what is the maximum width that two slits can be spaced which still permits the double-slit phenomenon to occur? Would this be a valid method of...

An object is accelerated close to c. Does the relativistic mass contribute to the sch. radius as seen by an observer? Is it simultaneously a black hole and not a black hole?

I am trying to figure out the minimum radius needed to avoid voltage breakdown. I found this from a Physics website: "The electric field near a conductor is inversely proportional to the radius of curvature of the surface." So if I know the voltage and the distance between the 2 metal...

there' s a problem that tells " estimate the radius of a planet that a man can escape it's gravitation only by leaping vertically upward..that density of the planet is assumed to be same as earth..." it seems to me that there's not enough information provided here to solve the problem...

Homework Statement I'm trying to figure out the radius of a circle that intersects two points on a right triangle. One side of the triangle is tangent to the circle and the other intersects it. I have attached an image that helps further explain what I'm talking about. Knowing what I have...

I'm trying to figure out the radius of a circle that intersects two points on a right triangle. One side of the triangle is tangent to the circle and the other intersects it. I have attached an image that helps further explain what I'm talking about. Knowing what I have listed in the image is...

Homework Statement An aircraft remains in flight by generating a force, called Lift, which acts to counter gravity. By design, Lift always acts in the “up” direction of the aircraft frame of reference (i.e., orthogonally to a lateral axis along the wings). An aircraft turns by banking its...

I have that \left( \frac{dR}{d \tau} \right)^2 = ( 1 - \epsilon)^2 ( \frac{R_{\text{max}}}{R}-1) describes the radius of the surface of a collapsing star in Schwarzschild geometry. I need to show it falls to R=0 in time \tau = \frac{\pi M}{(1-\epsilon)^{3/2}} So far I have rearranged to get...

Does centripetal acceleration increase with a greater radius? According to a = v^2/R, it does not. According to a = (omega)^2R, it does. So which is it? I think that as you go further out to a greater radius, speed also increases, and so a = v^2/R would also make sense in terms of a greater...