# Questions tagged [string]

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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### Does rope in a standing wave expand and contract as it moves between being straight vs sine?

Images of standing waves often show two people using a jump rope. The shape of the rope goes from straight to waves to straight, then a sine wave the other way and then straight again as it repeats. ...
21 views

### Forces Problem from Halliday, Resnick and Krane [closed]

To my knowledge, the net force on $m_1$ is $T - m_1 \cdot g \cdot \sin(\theta_1) = m_1 \cdot a$ assuming that the block accelerates up the incline. However, the solutions manual states that the ...
308 views

### Capstan equation with only one end of rope under tension

The capstan equation will give me the relation between the tension force at both sides of a rope wrapped around a cylindrical object, but what happens in this situation where the 'rope' is something ...
29 views

### Forces in a rope (tension) [duplicate]

I am confused with the concept of tension in a rope. Look a the diagram. Two forces are acting in a body, in this case the body is a rope, hence the total force in the rope should be zero, right? So, ...
1 vote
21 views

### Circular motion after tension gets zero

If we have an object rotating in a vertical plane, with a cord which cannot extend (has fixed length), what happens after the tension goes to zero? How do I prove mathematically that the trajectory ...
78 views

### Would the string break? [closed]

Thinking about the Bell's string paradox, I came to this thought: Would the string break - I mean a real string with some resistance -, if in the Bell's paradox we change the "constant proper ...
582 views

### Why does particle leave circular motion after string slacks?

If a particle is attached to a string and made to move in a vertical circle with initial velocity of $\sqrt{4gl}$ $m/s$ where l is the length of string, at some angle (approx $131°$ with the initial ...
166 views

### Tension in massless rope

We are learning Newton laws in the University and were given the following problem: In the system described in the image, the man is pulling two massless ropes with a force of $F$ each. We are ...
542 views

### Can you determine an action-reaction pair when tension acts on a string attached to a pulley?

I have been learning about tension and was doing some reading on trying to explain these forces at the intermolecular level and later also trying to see how it fits in view of Newton's third law- I ...
60 views

### Can someone provide the solutions to these questions asked in my exam in my high school [closed]

In the arrangement shown in the figure, initially the block of mass 'm1' is in limiting equilibrium. The coefficient of friction between the block of mass m1, and floor is 'u' Now the particle of mass ...
27 views

### Problem related to adiabatic invariants [closed]

A simple pendulum is oscillating in the gravity field, while its length slowly decreases with time. Determine amplitude of the small oscillations $A$ of the bob, when length of the oscillating part of ...
24 views

### Tension in Atwood machines [closed]

Assume massless pulleys and strings. Going from up to down, pulleys are labelled 1,2,3,4. I am trying to grasp how tension is passed from string to string. My intuition tells me that starting ...
1 vote
764 views

### Ball suspended on elastic string (finding tension)

A ball (of mass $m$) is suspended by an elastic string. It accelerates upwards with an acceleration $a$. Find the tension in the string. Taking upwards as positive, we have T - mg = ma \iff T = m(a+...
120 views

### Tension Problem (Classical Mechanics) [closed]

An exercise from my textbook revealed to me that I have some misconceptions about Newtonian mechanics. The textbook gives the answers to the questions, but I'm hoping someone can explain how it works ...
1 vote
44 views

### Why is the self-weight of a cable not uniformly distributed?

I have learned that a free cable that is hanging with only its self-weight to consider will form a caternary while a cable with a uniformly distributed load forms a parabola. Why is the self-weight of ...
1 vote
309 views

### Can I shorten the resonant length of a tight wire by moving its endpoint in phase?

A stretched string, tube or wireless antenna has a resonance fixed by the velocity of the wave (sound in air, metal, electrical wave etc.) and the length of the object. The fundamental occurs when a ...
130 views

### Finding force in a constraint motion problem [closed]

I have a doubt regarding the correct method to solve this question. A bead of mass $m = 0.5kg$ which can slide along a smooth horizontal rod is attached to one end of a light inextensible string of ...
384 views

### Amplitude of a wave, and boundary effects

I am curious as to what causes a discrepancy in the amplitude between the incident and the reflected/transmitted pulse. (* For instance, in the first image, the incident pulse seems to be of greater ...
4k views

### Laws of motion while climbing a rope

I'm a little confused with the application of laws of motion on a man climbing a rope. Suppose a man of mass Mg is climbing a rope with an acceleration a. Rope is massless. Now if look through the ...
197 views

### Tension in a string attached to a spring with deformation at a point

I am trying to calculate the tension in a string in the configuration shown in the diagram below. Here is a verbal description of the setup: The string is fixed at one end with the other end connected ...
1 vote
48 views

### Virtual work method in pulley [closed]

The problem illustrates two pulleys whose two ends are going downward with velocity $v$. The problem was about finding the velocity of the point $X$ i.e the point where the strings of the two pulleys ...
468 views

### Tensile force on a metal cable

Suppose you have a steel cable that has a certain elastic limit. Then I decide to use this cable to support an elevator of a certain mass $m$. Certainly the cable goes under some stress due to the ...
634 views

### How can we know direction of blocks in pulley systems?

How can we find the direction of acceleration in pulley systems so that we can write equation of motion for different parts of the pulley system. Do we have to assume acceleration in some particular ...
676 views

### How does Tension, or length, on a string effect overtones?

In a recent experiment I saw that notes with the same pitch, played on strings of varying tension, have a different number of overtones. The pitch is kept constant by altering length. Less tension ...
197 views

### Does the rope stretch when the pulley of Atwood's machine is accelerated?

Let's say I've an Atwood's machine in which I have two point masses which are different. Now, when I accelerate the pulley, the two masses accelerate at a different rate which can be shown by ...
1 vote
158 views

### Equivalent length of a simple pendulum

i was solving some question based on harmonic oscillations and a question popped up: If the angle between the the wires and the surface is 45 and the mass of the bob is $m$ calculate the time period ...
244 views

### Calculating weight needed for a fixed pole

Imagine a game of swing ball, where the rope is 1m long, and the ball weighs 1kg. How do you calculate the weight that the pole has to be so it does not get pulled over, assuming it is not burried in ...
51 views

### Asserting $\frac{\partial y}{\partial x} |_x = \frac{T_{1y}}{T_{1x}}$ for wave characteristics on a string

There have been two issues I've been running into trying to understand the derivation of wave speed on a string, as well as wave energy transport on a string, which have boiled down to the same gap in ...
75 views

### Deriving wave equation of string without approximation

When deriving the equation for a standing wave of a string, we often approximate that the tension at all points in the wave is constant. but I want to derive the equation without the approximation. I ...
4k views

### Neglecting friction on a pulley?

So, this is how the problem looks: Plus, the pulley is suspended on a cord at its center and hanging from the ceiling. You're given masses of the objects, mass of the pulley and it's radius. And your ...
1 vote
54 views

### Catenary curved string with differing linear densities - Linear density distribution

Do you guys know if there's some kind of weight distribution that fits a problem like this one? Let there be a string with two different sections with different linear densities, like the following ...
27 views

### For two strings tied together: Why does a sinusoidal incident wave give rise to sinusoidal reflected and transmitted waves? [duplicate]

I am reading Griffiths' Intro to Electrodynamics (Section 9.1.3 Boundary Conditions: Reflection and Transmission) where he analyzes the case of an incident wave sent down a string that is tied to ...
21 views

### Details on the string theory being a quantum gravity theory [duplicate]

So since string theory is a quantum gravity theory, how can we derive from string theory to Einstein gravity equation when $\hbar \rightarrow 0$, as what we did from quantum theory to classical theory?...
1 vote
567 views

### Understanding conservation of energy in a pulley problem

I am trying to check if my understanding of conservation of energy is correct. Imagine a pulley problem like so with $m_2$ heavier than $m_1$ and the pulley is ideal (in the original problem I ...
1k views

### Can the wavelength of the standing wave be different from the wavelength of the sound it emits?

I have a question about standing waves on strings. I'll try to explain the best I can, I searched and researched the whole day yesterday but I am confused still: Every frequency has a single, and ...
1 vote
75 views

### Why is the potential energy of a suspended rope proportional to the stretch?

In A. Zee Einstein Gravity in a Nutshell, when he is talking about variational calculus on page 113, he gives an example of a suspended rope. To calculate the total potential energy due to tension, it'...
67 views

### How does a string "distribute" tension?

This question deals with a massless, inextensible string. The problem arises with the question below. We know by Newton's third law that the force a body will apply on the string will be equal to the ...
87 views

### Can anything be a system?

I was doing some problems on Newton's Laws of Motion, and I found out that the solution arbitrarily considered anything as a system. For example, in this question on pulleys, the solution simply took ...
1 vote
426 views

### Question regarding tug-of-war and tension

I am having a hard time understanding these questions regarding tension$-$ Is the tension in a rope uniform in a tug of war? If yes, then who wins the game? If no, doesn't that violate Newton's ...
57 views

### What is not inverted when a string wave reflects with phase reversal?

When a wave reaches a boundary and it is reflected, it may happen that, if certain conditions are fulfilled, there is a phase reversal (180$^\circ$), so that what came as a crest becomes a trough and ...
1 vote
123 views

### Some confusing points about Bell's spaceship paradox from a video

I was looking this video about Bell's Spaceship Paradox on Youtube titled This Paradox Took 17 Years To Solve. It's Still Debated. Please note that the video starts at the segment I have a question ...
1 vote
146 views

### Energy conservation in a system of two bodies

I have no idea why my previous post was marked as a homework question where the solution was clearly visible. I was asking to clear a concept of mine regarding system of bodies. However,i will keep ...
55 views

### How can I calculate the number of nodes on a plucked string?

Given the length of the guitar string, can you predict the number of nodes that would exist on that string? My textbook says that there are an infinite number of harmonics that can be created when a ...
167 views

### Implications of massless pulleys in Atwood machines

Consider the double Atwood machine below: I understand the classic approach to a solution for the acceleration of each mass involves setting the tension in the upper string equal to twice that of the ...
28 views

### Why is the tension force in a rope with two different forces acting on it uniform? [duplicate]

Let me explain myself. Imagine a massless rope over a pulley, two weights m1 and m2 attached to the ends of the rope. M1's weightforce (m1xg) exerts a force on the rope, call it T1. On the other end ...
1 vote
54 views

### Is it possible to find Tensional force from Lagrangian?

The Lagrangian principle is easier to solve than any kind of problem. But, we always "forget" (not really, but we don't take it into account directly), of Tension in a system when looking at ...
42 views

### How does the tension exactly act on the pulley?

Everyone says that $T_1$ and $T_2$ will act on the patch of pulley wrapped by the string. So do they act on arcs $AB$ and $CD$ respectively? If not, then how do they act? And if $T_1 = T_2 = T$, they ...
1 vote
1k views

### Finding Tension in an Elastic String?

I know that this is a homework type question and I'm not asking a particular physics question, but I'm really desperate for help. Here's the question: I tried to divide the string to 2 parts with $O$...
Suppose we have an extensible massless string satisfying Hooke's Law, tied to a wall at one end and going over a 'frictional pulley'. Now if we tie the other end with a mass $M$, the total length of ...
In preparation for the SAT Physics Subject Test, I have been doing extra practice problems. This one states: A garment bag hangs from a clothesline. The tension in the clothesline is $10 \,\text{N}$...