String Definition and 1000 Threads

Homework Statement 10kg is attached to the end of a string, which is thread through a vertical tube. The string and the tube always make a 90 degree angle. The distance from the tube to the mass is R and the velocity at which it rotates is V. How much work is done to shorten the distance...

Homework Statement Consider a constant volume elastic string. A change in internal energy of the string is given by dU = TdS + fdL. The elastic string obeys the following two equations; $$\left(\frac{\partial f}{\partial L}\right)_L = \gamma_1 T\,\,\,\,\,\,\,\,\,\,\,\left(\frac{\partial...

Hi all, Could someone please help me understand a small but significant step in the derivation of the wave equation for a string with stiffness. I am trying to follow the notes here: http://courses.physics.illinois.edu/phys406/Lecture_Notes/Waves/PDF_FIles/Waves_2.pdf The statement...

Homework Statement a 0.60 kg sphere rotates around a vertical shaft supported by 2 strings, as shown. if the tension in upper string is 18N calculate. a) tension in lower string? b) rotation rate (in rev/min) of the system. Homework Equations The Attempt at a Solution...

I just want to make sure I understand the normal modes of a vibrating system of particles with discrete spacing. I have tried to drawn what I understand as the lowest and highest frequency mode of the standing waves. Is the drawing correct? Edit: actually I have drawn the maximum frequency where...

Homework Statement A string of length l has a zero initial velocity and a displacement y_{0}(x) as shown. (This initial displacement might be caused by stopping the string at the center and plucking half of it). Find the displacement as a function of x and t. See the following link for...

It seems many people in Science have gravitated towards some form of a multiverse. Whether it's a Cyclical Universe or some version of the Many Worlds Interpretation. The question is where's the evidence? I do think there's some evidence that points to this conclusion. If you look at the work of...

Homework Statement For a string of length 100m with fixed ends, a pulse is traveling to the right at a speed of 40 m/sec. The pulse has a wavelength of 2 meters and an amplitude of .1 m. Homework Equations y=A*Sin(kx-wt) ((where w is omega)) \lambda=2*pi/k frequency=w/2pi...

1. A cylindrical string is made out of thin wire. The distance between every loop of an unstretched spring is equal; The radius of every loop of the spring is r = 4 cm; The length of an unstretched spring is l = 20 cm; The mass of the spring is m = 50 g; The spring is hung on the ceiling by a...

Homework Statement A guitar string of diameter 0.6 mm and length 0.82 m is subject to a tension of 153 N. If the string stretches an amount 0.36 mm, what is Young's modulus of the string? Homework Equations Y=Stress/Strain Stress=F/A Strain=Amount of stress/Original Length The Attempt at a...

Lets say we have a ball on a string and we spin it around. The ball will undergo circular motion. The tension in the string is what provides the centripetal force, directed inwards. Then what would be the force directed outwards? (According to Newton's third law of motion). It can't be...

I'm a 10th grade high school student, but before you judge me I would like to inform you that I have a 127% (thanks extra credit) in my Advanced Physics class. I was reading the textbook as I usually do in my free time and I stumbled across a section on String Theory, I read through the chapter...

Hello, PhysicsForum, I haven't posted a physics question, mainly because I don't have mechanics classes anymore :( But, studying on my own, I found this problem on the web with the solution: «61. A 2.0-kg box is attached by a string to a 5.0-kg box. A compressed spring is placed between...

Hello, could someone look over my answer? I am not very confident I did the problem correctly. Homework Statement A 76-kg ball is tied to one end of a massless string of length The other end of the string is tied to a nail in the center of a table. The ball is set into uniform circular...

Consider N atoms separated by springs of force constant C. If one writes up the N linear differential equations for the displacements of the string, you find that the solutions are traveling wavse of the form exp(ikx) and on finds a dispersional relation of the form: sin(...), which means that...

Hi, please could someone explain why a wave pulse traveling down a rope inverts when it strikes a fixed boundary. Is it something to do with conservation of momentum?

Homework Statement Two objects are made of identical material and are tied together with string. The first object has a mass of 5.0kg and the second object has a mass of 3.0kg. Students measure the maximum force of static friction as 31.4N to move both objects across a horizontal surface. a)...

Where can I learn string theory online with the math and everything? ANY help appreciated. Tanks in advance. Ps I'm looking for links, I really can't afford books. I'm a high school student. I know the principles but haven't attempted any math above the Schrödinger equation for a quantum...

My plot seems wrong so I am not sure what the problem is: (a) mistake in sol (b) mistake in coding. A clamped, uniform string under tension \(T\) has length \(\ell\). The string is struck in the middle, giving an initial tranverse velocity distribution \[...

Hey! So If I have a stretched string of length L fastened at one end, and I am moving the other end sinusoidally, will a standing wave appear ONLY if I move the other end with one of the normal-mode frequencies of the string? If not, will the resulting wave be a moving wave which is a...

Hi guys, I am ready to apply for PhD and one of my targets is STONY Brook (actually the only one in the USA since it won't require me to take any tests). Background: a) Undergrad at Lancaster University, BSc Theo. Physics b) Master's degree in Theo. Physics UAM/IFT in Madrid under...

So I have one attempt left and want to make sure my answer is correct, so double checking me would be super awesome! You are given a pendulum composed of a 0.030 kg mass on the end of a 0.42 m long massless string. The pendulum is moved 25° from the vertical and released. Find the tension in...

Just to clarify, if a string has a threshold of 100N, can the string be bent so that the tension in different parts individually doesn't exceed 100N yet the total force of the tensions do? My question arises because of this question: http://imgur.com/90NGY5p http://imgur.com/ObRq5QM...

I take it strings are too small to have "connectors" on their ends, there is no glue etc. so how could strings combine to become larger particles like bosons. I have never heard anyone describe the reason for the extra dimensions that string theory says are there. Could it be that these...

Hi there! S-matrix is Path Integral with Vertex Operators inserted. I know how to compute Shapiro-Virasoro amplitude. So I don't have problems with calculations but with understanding. In this calculations formalism of 2-dimensional CFT is used. But there is no S-matrix in CFT, only...

According to string theory there are an extra 7 spatial dimensions curled up at every point in space. They are so small(Planck length) that nothing can move through them and are completely undetectable. My question is this: Does string theory allow for these dimensions to uncurl and become...

Homework Statement A block of mass M has a string of mass m attached to it. A force F is applied to the string and it pulls the block up a frictionless plane inclined at angle θ to the horizontal. Find the force the string exerts on the block. Homework Equations F = ma The Attempt...

1. A violin string is 35 cm long between its fixed ends and has a mass of 2.0g. The string sounds the note A4 (440 Hz) when played. Homework Equations v=\sqrt{}F/ρ The Attempt at a Solution I calculated ρ, mass per unit length, to be .0057 kg/m but do not know how to find the...

Homework Statement http://home.phys.ntnu.no/brukdef/undervisning/tfy4145/ovinger/Ov03.pdf look at "oppgave 5". In the problem, you have a massless string with 4 uniform masses attached symmetrically, and you are supposed to show that the implicit equation for x (and x = cos(alpha)) is correct...

I would like to calculate the maximum distance, crest, a guitar string will travel at it's center when plucked in order to determine how high the string needs to be on the fretboard to avoid striking parallel frets and thus avoiding "fret buzz". Example: 0.762 mm string thickness with...

A 10g mass is suspended from a string and immersed in a beaker of liquid(Weight of beaker and liquid = 500g). A boy hold the string with his hand not letting the 10g mass touch the bottom of the beaker. (let upthrust generated by mass be X Newton.) Qn: what would be the reading on the...

Hey everybody, I have a few questions about membranes in string theory, so here it goes. What is meant by the membrane in the cyclic model, from my understanding it means that branes in an ultiverse collide, and create there own universes, would this mean that branes could collide in our...

Homework Statement The linear mass density in a string is given by μ = μ0[1 + cos(x/R)] where R is a constant. If one averages this density over the large size L it becomes uniform: <μ> = μ0, where <…> means averaging. What is the minimum size L (in terms of R) such that the density can be...

I thought about this when hanging my belt on to the towel holder. If i put too much of the belt on one side, that side would fall down. Why does this happen? Shouldn't the towel hanger just put up an equal force to the total weight of the belt keeping it up? I understand a little when we say...

The presence of a cosmic string does not lead to gravitational attraction of a particle placed some distance away from it. But it affects the geometry of planes orthogonal to the cosmic string, such that the circumference of a circle traced out when moving around it at a distance r is given by...

Homework Statement A solid uniform 45.0 kg ball of radius 0.16 m is supported against a vertical, frictionless wall using a thin 0.30 m wire of negligible mass. Find the tension in the wire. Homework Equations Sinθ = opposite/hypotenuse Cosθ = (m*g)/T or T/(m*g); I'm not...

Why is tension in a massless string same throughout its length?

Hi all! I am ready for applying for my PhD which I want to be on String Theory and in Europe. I am finishing my master's degree in Theoretical Physics and currently I am researching Holographic Renormalization for asymptotically non-AdS space-times. I am interested in all aspects of String...

Are the strings in M-Theory impermanent, do they decay for example?(I am not a physicist, curious from a philosophical perspective)

Why string field theory doesn't explane a black singularity but its called the theory of everything? It just explanes quantum gravity not why the universe exists or why we exist, what I am tring to say is that it should not be called the theory of everything.

... due to whatever. What has the effort provided besides showing that the universe doesn't work a certain way? Assuming it has aided in other areas of physics and mathematics. Any examples? Thanks.

I just can't get why for a massless inextensible string passing around a frictionless pulley we easily take T1=T2 (in fig.).My profs. never did explain this & jumped on further & when i ask them they won't answer saying it was very basic and other students say it's obvious. pls. help also pls...

1. If two books are tied together with string and one is pushed off the edge of a table. What the acceleration of the two books? Zero g/2 g a value between zero and g a value that could be greater than g 2. gravity acceleration laws 3. G, because gravity acceleration is independent of mass

Homework Statement Given that the stretched length of a string is Δx(1+1/2(dy/dx)^2) show that the potential energy per unit length is equal to 1/2F(dy(x,t)/dx)^2 Homework Equations potential energy = kx^2 cos(kx-wt) idk really... The Attempt at a Solution The fact that the...

This was just posted on arxiv. It seems to be of general interest so here's a thread in case anyone wants to discuss it. http://arxiv.org/abs/1308.1977 Holography without strings? Donald Marolf (Submitted on 8 Aug 2013) A defining feature of holographic dualities is that, along with the bulk...

what are the research prospect of doing a phd on string theory in India

Laurent Freidel is working on string theory again. His earlier paper, with Krasnov and Livine, which had a remark on the subject was Holomorphic Factorization for a Quantum Tetrahedron http://arxiv.org/abs/1307.7080 Born Reciprocity in String Theory and the Nature of Spacetime Laurent Freidel...

From looking at the Wikipedia entry on string theory I gather that it is found that any given physical model implies two Calabi-Yau spaces. Perhaps one space gives rise to a sector of particles with left-handed weak interactions and the other gives rise to a sector with right-handed weak...

Hi everyone, I was wondering what forces would counteract the force of gravity on an object which is spinning horizontally on a string. I realize its a component of the tension, but how does the force come about? Is this force also the reason that the object's plane of rotation rises when we...

Homework Statement Object A has mass 90.0 g and hangs from an insulated thread. When object B, which has a charge of +130 nC, is held nearby, A is attracted to it. In equilibrium, A hangs at an angle θ = 7.20° with respect to the vertical and is 5.00 cm to the left of B. (a) What is the charge...