This tag is for non-relativistic material strings, such as, e.g., a guitar string. PLEASE DO NOT USE THIS TAG for relativistic strings and string theory.

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2
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2answers
50 views

What happens if I slowly lower a dangling object into a black hole?

I could've sworn I've seen this question before, but I couldn't find it. Suppose I have an object on the end of a really long string. I can slowly lower it near the event horizon of a black hole, ...
-2
votes
0answers
31 views

What is $T_1$ and what is $T_2$ in Capstan law?

How do I determine which force is which (T1 or T2) in the Capstan law? In case there is no rotation and in case there is rotation of the capstan.
1
vote
3answers
75 views

What is the physical meaning of reduced mass?

If we stick two block masses by a string and pass it over a pully and let the blocks free then mathematically we can obtain that the whole weight on the pully is more if the blocks are kept at rest, ...
0
votes
0answers
42 views

Plucking Guitar Strings

I was given this prompt: A musician frets a guitar string of length 1.5 m at x = 0.28 m with one finger, and simultaneously plucks the string at x = 0.14 m with another finger (raising it to a height ...
6
votes
3answers
91 views

Transverse simple harmonic wave travelling in a string

This question came in my exam. My Attempt: I thought that the tension will not vary in the string because since we know that velocity of wave in a string is given by $$v=(T/m)^{1/2} $$ where $v$ ...
1
vote
4answers
546 views

Another layman blackhole question, pulling one end of a string out from behind the event horizon

No long explanation is needed, What would happen if I were to allow one end of a rope to fall past the event horizon of a black hole while I held the other end? Would I be able to pull it out? Would ...
7
votes
1answer
207 views

Equilibrium for a rope hanging in a Schwarzschild spacetime

Update: Trimok and MBN helped me solve most of my confusion. However, there is still an extra term $-(2/r)T$ in the final result. Brown doesn't write this term, and it seems physically wrong. Update ...
-1
votes
1answer
54 views

What will happen to Earth if it's tied to a black hole thru a really strong string?

Imagine a very strong string (with infinity as as its breaking point) attached to earth very strongly and the other end is put inside a black hole, What will happen to Earth? And the string? Will ...
3
votes
0answers
27 views

Rope waves with a twist

In the picture you see a person walking a slackline. A slackline is a tensioned flatband of polyester. Typical tensions are between $1kN$ to $15kN$ depending on the length of the line. The lines ...
1
vote
1answer
185 views

Can two bodies of different mass attached at ends of string passed over a frictionless pulley produce equal tension on both sides?

In my textbook there is given a case that to calculate acceleration and tension produced in string when string is attached at it's ends with two bodies of masses such that $m1>m2$ and the tension ...
0
votes
0answers
21 views
0
votes
2answers
36 views

Force on a Massless String

Suppose we are just pulling a block with the help of a string which is massless. Now since the mass of the string is 0 the force exerted by us is transmitted without being diminished. So the equation ...
2
votes
0answers
16 views

Which supersymmetry principles make the axio-dilaton field in F-theory holomorphic?

I am following the lecture notes on F-theory by T. Weigand . On page 7 he states that when considering F-theory as the strong coupling limit of type IIB orientifolds with D-branes, the axio-dilaton ...
2
votes
3answers
2k views

When is tension constant in a rope?

Suppose we have a massless rope with pulling forces applied at each end. In which scenarios is the tension in the rope constant throughout? For example if there is a knot in the rope the tension is ...
4
votes
1answer
77 views

Why do headphones tangle themselves whereas shoe laces untie themselves?

Why do headphones tangle themselves whereas shoe laces untangle or untie themselves? Why aren't we using the phenomenon to create headphones that tangle less and shoe laces that untie less?
7
votes
1answer
631 views

Why do flat cords tangle less in my pocket?

We've all experienced this: put a pair of earbuds in your pocket, and when they come out, they're a tangled, knotted mess, cf. e.g. Why do earphone wires always get tangled up in pocket? However, you ...
0
votes
1answer
26 views

Pulley inertia momentum of inertia

Considering a pulley with some mass, or some friction, How can its inertia (or momentum of inertia) influence the tension on 1 rope? Which part of the rope is influenced? Before or after the pulley?
3
votes
1answer
322 views

Flux compactification

How flux compactification solves the moduli space problem in string theory? Please provide some details and, if posible, an example.
0
votes
1answer
79 views

Atwood's Machine [closed]

Using an Atwood’s machine, how will the acceleration change if the sum of the two unequal masses (total mass) are kept constant while the mass difference changes? Using an Atwood’s machine, how will ...
0
votes
0answers
19 views

Systems of connected particles: Pulleys [closed]

Q. A light extensible string is fastened at one end to a point in the ceiling. It then passes under a smooth moveable pulley P of mass 8kg then over a smooth light fixed pulley. A second particle Q ...
1
vote
1answer
87 views

Spinning a string with a mass on the end. What makes the mass rotate parallel to the ground? [closed]

Say you use your hand to rotate a string with a mass attached to the end. The string will first become taunt and then the mass and string will move upwards until they are spinning parallel to the ...
0
votes
1answer
27 views

Rope tension definition

What is the exact definition of the tension of a rope? Here http://web.mit.edu/8.01t/www/materials/modules/chapter08.pdf the following definition is given The tension $T(x)$ in a rope at a ...
0
votes
0answers
26 views

Ramond-Ramond potential and field strenght

I have a doubt about R-R potential in Superstring theory. The known facts are (according many books, for example "Basic Concepts in String Theory" by R. Blumenhagen, D. Lüst and S. Theisen): in the ...
0
votes
2answers
626 views

Tension in string and gravitational force on bob relative strength

When calculating time period of simple pendulum (an approximation of SHM at small amplitudes) we take gravitational force greater than tension in string and resolve gravitational force in two ...
0
votes
1answer
45 views

What's the required tensile strength for a wire?

I want to horizontally stretch a 50 meters wire rope and slide 100 kg object from side to side. What should be the minimum tensile strength (or carrying capacity) of the rope to be able to hold the ...
5
votes
4answers
813 views

Wave reflection and open end boundary condition intuition

I need to understand one seemingly simple thing in wave mechanics, so any help is much appreciated! When a pulse on a string travels to the right toward an open end(like a massless ring that is free ...
3
votes
1answer
30 views

Slackline tangling

This question is about random formation of knots in a systematically tied rope. I will give some background, hope that does not make it off-topic. In climbing (and sailing) one has to store very long ...
0
votes
4answers
3k views

Is tension always constant throughout a rope of mass in equilibrium?

Let's say we have a meter stick with a single rope attached to it. One end of the rope is attached to one end of the meter stick, the other end of the rope is attached to the opposite end of the meter ...
2
votes
2answers
255 views

Why does, at one time, tension balances the weight but at the other time don't balance it?

Everyone is accustomed to many set-ups of Atwood machine; sometimes the question asks about acceleration of the blocks or so; sometimes they ask about tension etcetera. But one thing I couldn't ...
4
votes
4answers
1k views

What Keeps a Pendulum Moving In a Circular Path?

From the figure, we know that $F_{net} = mg\sin\theta$. Now, this force $\vec{F_{net}}$ is in the direction of the velocity $\vec{v}$ of the bob, both are tangent to the path. Therefore, the net ...
2
votes
1answer
243 views

Question about force in transverse waves on a string

In deriving wave equation or power transmission of wave transmitted by a string, it is usually stated (with some assumptions) that the transverse force on a point of the string is proportional to the ...
45
votes
1answer
7k views

Why do earphone wires always get tangled up in pocket?

What is the reason? Is it caused by their narrow shape, the soft material, walking vibration or something else?
24
votes
7answers
11k views

Why Won't a Tight Cable Ever Be Fully Straight? [duplicate]

I posted this picture of someone on a zipline on Facebook. One of my friends saw it and asked this question, so he could try to calculate the speed at which someone on the zipline would be going ...
1
vote
2answers
1k views

Can we define tension in a string as the reactive force produced in a string being pulled at both ends?

In my textbook, the definition of tension was given that Tension is the reactive force which exists when string is being stretched at its both end. After it there was a case given that to calculate ...
0
votes
2answers
417 views

Why is the net work done in a pulley-string system zero?

In any pulley system, where the pulleys and strings are massless and frictionless, why is the net work done by Tension zero?
10
votes
2answers
1k views

How can you make harmonics on a string? [duplicate]

For an oscillating string that is clamped at both ends (I am thinking of a guitar string specifically) there will be a standing wave with specific nodes and anti-nodes at defined $x$ positions. I ...
1
vote
0answers
26 views

Standing Waves in a String of two Linear Densities

Given a string with sections of two linear densities like this: Does the point where the two linear densities meet have to be a node if a standing wave is produced? Are there alternatives? Could I ...
1
vote
1answer
32 views

Dependence of tension (considering a pulley system) on the mass of loads

Consider the diagram below All circles are pulleys, which are fixed at the ceiling. M represents an engine (with a certain power) that is pulling the cable. C and D are weights. The acceleration of ...
1
vote
2answers
47 views

Condition for looping the loop

Consider a ball tied to a string and it is imparted a velocity we have studied that condition for looping the loop is that tension at the uppermost point must be zero, but why is this condition ...
1
vote
4answers
86 views

When is tension positive?

A 5kg mass is hanging from the roof of an elevator accelerating downward at a speed of 1.65 m/s^2 what is the tension of the string (ignore friction, string mass, and air resistance) ? I used this ...
0
votes
1answer
43 views

Finding mass attached to the string

I'm given the following problem: One end of a string with a linear mass density of 7.60* 10^-4 is connected to an oscillator with a frequency of 50.0 Hz. The other end is connected to a hanging ...
0
votes
1answer
59 views

Problem in constraint equations

In this, if I want the acceleration constraint between $M$ and $2M$, I write $AM+2AB$=LENGTH OF STRING, which on differentiating twice gives $a_{m}=2a_{2m}$(which turns out to be correct). However, ...
3
votes
2answers
64 views

shape formed by a stiff string with ends pinched together [closed]

Suppose I have a string of length $L$ with a bending energy given by $$E=\frac{1}{2}\epsilon \int_0^L ds\, (\mathbf{R}''(s))^2 $$ Let's say I form a bight with it by pinching the ends together, ...
0
votes
3answers
63 views

Conditions for the tension to vary in the rope

What are the conditions for the tension to vary in the rope. I have read below conditions 1. rope has to have some mass 2. rope is accelerating I get the 1st ...
1
vote
1answer
70 views

Normal Ordering in String Theory: Polchinsky vs. all others

Polchinsky defines normal ordering in string theory as: $$:X^\mu(z,\bar z)X^\nu(w,\bar w): = X^\mu(z,\bar z) X^\nu(w, \bar w) + \frac{\alpha'}{2} \eta^{\mu\nu} \log |z-w|^2$$ and for more ...
3
votes
1answer
127 views

Moments of vibrating string

I have to calculate first 10 moments for vibrating string with damping, but I don't know how to do it. I read about moments and in definition they mention linear system $$x'=Ax+Bu, \qquad y=Cx$$ with ...
0
votes
1answer
42 views

Tension in a vibrating loop

Consider a super basic 1D vibrating string, with standing waves on it. The string has length $L$, and the wave propagates at a velocity $v$. The fundamental frequency $f_1$ is given by $$f_1 = ...
1
vote
2answers
90 views

Why can we assume, when dealing with tension, that the mass of a rope is $0$ but still assume that there are forces on it?

I started studying tension and I can't understand the following concept: If I have two objects $A,B$ collegated by a rope, where $A$ applies a certain force $\vec{F}$ on it, I would have that the ...
2
votes
2answers
378 views

How can Hilbert spaces be used to study the harmonics of vibrating strings?

The overtones of a vibrating string. These are eigenfunctions of an associated Sturm–Liouville problem. The eigenvalues 1,1/2,1/3,… form the (musical) harmonic series. How can Hilbert spaces be ...