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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How can I accelerate the linear speed of a spinning rock on a string when the rope can exert no net torque on the rock?

If I take a rock attached to a mass-less rope and start spinning it over my head (or on a friction-less surface, I don't think it matters) I can accelerate the linear speed of the rock (I can spin it ...
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2 votes
2 answers
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Solving this problem using the Work-Energy Theorem [closed]

A block is tied to a string wound on a cylinder of mass $m$ and radius $r$, (Through a pulley) which can rotate about its axis on a massless mount placed on a smooth surface. The system is released ...
1 vote
3 answers
170 views

Plucked string eigenvalues/harmonic frequencies: integer multiples (or not)

I'm trying to derive a model of a plucked string from Newton's second law. My derivation results in $$ω_n = C\cdot\sqrt{n},\, n=1,2,3\dots\text{integer}$$ I think it should be $$ω_n = C\cdot n,\, n=1,...
-1 votes
1 answer
78 views

Work done by force and tension of a string on a body

A person lifts a box using a string passing over a smooth pulley and inclines to the vertical with a 30 degrees angle. The tension force in the string is 120 newton to rise the box 3 meters. Is there ...
0 votes
1 answer
88 views

Two-Body Problem on a Frictionless Table with a Hanging Mass [closed]

Here's the situation. There are two boxes connected by a string. Box A is on a frictionless table. A string attached to Box A runs over a frictionless pulley and is attached to the hanging Box B. ...
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4 votes
2 answers
214 views

Why does the classic wave equation for a non-relativistic string look like the Klein-Gordon equation?

There is a very old equation known as the "wave equation". It's an ordinary classical non-relativistic differential equation which applies to just about every kind of ordinary wave you can ...
5 votes
5 answers
317 views

Why can we use Newton's second law for a massless pulley in this problem?

We have the following configuration of pulleys: The problem states that neither the rope, nor any of the pulleys have mass and they rotate without friction. The task is to find the acceleration of ...
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2 votes
1 answer
73 views

How do standing waves produce a note?

I just learned standing waves in class. And I know that fundamental frequency is the minimum frequency with which a standing can exist on a string. Then we talked about the role of standing wave in ...
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0 votes
1 answer
58 views

Strength of intermolecular forces as a function of distance

In Introduction to Mechanics by Kleppner and Kolenkow they talk about the tension force of a string and its microscopic origins. They explain how applying a force on a string slightly increases the ...
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-1 votes
3 answers
114 views

I am puzzled about the difference between these two situations [closed]

A block of mass $m=20kg$ stands on a frictionless horizontal surface. It is pulled by a rope, which passes through an ideal pulley. The rope is connected to a lifting block with a weight of $W = 50N $...
1 vote
1 answer
48 views

Show that this expanding cylinder will unravel this loop

Below is a really hard physics(?) problem which I honestly don't even know how to begin. I thought of it when reading a knot theory book. Below in the picture, you see the projection of an unknot (a ...
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1 vote
4 answers
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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 ...
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0 votes
2 answers
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How is length of string and frequency of sound related in musical instruments like guitar, violin etc? Also differentiate between note and tone

I read a sentence that a guitarist set his strings before performance then he is changing frequency of sound. I was wondering in which case frequency will be more, if length of string is large or ...
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2 votes
1 answer
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Intuition for normal modes of a beaded string

These questions are inspired by the following the paper http://www.soton.ac.uk/~stefano/courses/PHYS2006/chapter7.pdf on 'Normal Modes of a Beaded String'. Problem Statement Given a recurrence ...
2 votes
1 answer
89 views

Is the frequency of a vibrating string equal to the frequency of the sound it creates?

Is the frequency of a vibrating string equal to the frequency of the sound it creates? For example, if a string is vibrating at 440Hz, would the sound it creates be 440Hz as well? Furthermore, would a ...
0 votes
1 answer
37 views

Tension vs. Temperature in a stretched string

Is there a nice way to express tension in a stretched string of fixed length (like a piano string) as a function of temperature?
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1 vote
0 answers
35 views

The effect of a temperature change on the fundamental frequency of a stretched string

I am curious about the effect of temperature on the frequency of say, a guitar string (stretched under a tension $F_T$ and of fixed length $L$). I wonder if someone here could check my work. First of ...
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1 vote
1 answer
65 views

Question about fundamental frequencies

For a string fixed at both ends, with a fundamental frequency of 440Hz, can there be a harmonic when a wave of frequency 220Hz is sent across the string? my book says no, but I disagree; can't ...
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0 votes
1 answer
41 views

Why tension gets lower in rope?

If we increase the force, F on m1 then the tension gets smaller. I want to visualize why tension is getting smaller without the mathematics .Is there any change in connecting rope which causes change ...
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0 votes
1 answer
43 views

What is $g$ for a bob hanging from a string?

Imagine a bob hanging from a string. Now, let's say that you pull the string to the right (or left, doesn't matter), and then allow it to fall freely. Will the gravitational acceleration g be the same ...
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1 vote
0 answers
33 views

Is there a relation between eigenvector and amplitude for a beaded string

I have a string fixed at both end with 5 beads. At $$t=0$$ $$v_p=0$$ where $p$ is the index for each bead and their initial displacement are $$(3,0,\sqrt{3},2,2)$$ I have to find the amplitude for the ...
0 votes
2 answers
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Velocity of bead when a light inextensible frictionless cord becomes taut. (Pathfinder methods of impulse build up 3rd question)

The complete question is "A thin light inextensible frictionless chord of length $l$ wearing a small bead is tied between two nails that are in the same level a distance $(0.5)l$ apart. ...
-1 votes
1 answer
232 views

Find Potential energy of a hanging chain

A chain of Length L is fixed at one end to a point and the rest of the chain is hanging such that the other end of the chain just touches the ground. Find the potential energy of the chain given its ...
2 votes
1 answer
63 views

If a point mass on a string starts at the bottom of a circle with $v_0$, is it possible for it to reach the top of the circle with zero speed?

Consider a point mass on the end of a string of length $l$ near the surface of the Earth. Initially it is hanging straight down, but it has initial speed $v_0$, such that it will undergo a circular ...
0 votes
2 answers
179 views

Tension in rope between two objects

My first question is I wonder why there's no opposite tension acting the towing cable in the diagram above since the two tugboats are dragging the supertanker. I thought if one obeject is dragging ...
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2 votes
2 answers
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Is pulling a string instantaneous at both ends? Why is it or isn't it? [duplicate]

This is a question that has bothered me for quite some time but I don't have a clue where to start in researching it. Let's say we have a string which is arbitrarily long, light enough to not take ...
0 votes
1 answer
38 views

Hanging (without tying) a ring or any other object with a massless string

Suppose ends of a string are attached to two different points on a ceiling. If a ring is hung freely, why does that ring move to the mid point of the string usually? Is it because the tension along ...
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-2 votes
2 answers
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Force being equal at all points in ideal string

If a person pulls an ideal massless string, why do all points in the string experience the same force? How to prove this rigorously?
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0 votes
2 answers
127 views

Rolling a cylinder using a rope having one end fixed and another end mobile

A cylinder is being rolled(without slipping) with the help of a massless rope towards the left direction. An attractive force is effective on the cylinder towards the right direction. One end of the ...
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0 votes
1 answer
113 views

Find acceleration using Lagrangian [closed]

I was trying to find acceleration of $m_3$ using Lagrangian. Without speaking a lot I am just starting to show my equations. $$L=T-U$$ $$=\frac{1}{2}m_1\dot{x}^2+\frac{1}{2}m_2\dot{x}^2+\frac{1}{2}m_3\...
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1 vote
1 answer
125 views

Why we want the string to be massless in the ideal model of simple pendulum?

I couldn't think about a reason why the string must be massless. Wouldn't the assumption that the air resistance is negligible, the angle $\theta$ is small and the string is non-stretchable suffice ...
4 votes
1 answer
83 views

Pulley system with constraints

Now I need to find out the acceleration of pulley A. I know that (acceleration of a) = 2(acceleration of c) and the accelerations of A and C are in opposite directions using constraints. The solution ...
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4 votes
5 answers
142 views

Final position of weight hanging from two opposed pulleys on ropes

Let's say I have the situation pictured below. The red and green ropes are tied to immobile supports. The ends of the red and green ropes are attached to frictionless rings. The blue rope is tethered ...
0 votes
3 answers
128 views

Boundary condition on a finite vibrating string with forced vibration

Context Considering a finite string of length $L$. We suppose gravitation is negligible. The string is only moving transversaly, in $y$ direction, with small amplitude. The tension of a string is $T$. ...
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2 votes
1 answer
65 views

Motion involving Constraint relations

We have the setup as shown in the picture. Two blocks A and B are connected by a string that always remains taut. Block A is on a frictionless surface. Block B is being pulled downwards with a ...
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0 votes
2 answers
53 views

Tension in the given situation

Here two equal masses $m$ are hanging. We have to find tension in wire AB and wire CD. Assuming the tension in wire be $T$, I can't figure out why the tension in CD is 2 times to that of in wire AB. ...
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-2 votes
1 answer
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What is the motion path of each point on the rope? How is the tension calculated? [closed]

The blue line is the rope. Suppose point A of the rope moves upward and point B does not move, what is the motion path of each point on the rope? How is the tension calculated?
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1 vote
2 answers
96 views

Friction and Newton's Laws of motion

I came across the following problem. Ok, I thought that assuming there is no friction between blocks B and C, when the blocks B and A will move, the block C will go to the right due to the force by ...
0 votes
2 answers
64 views

How much does string material elasticity affect tension at pitch for a stringed instrument?

In introductory physics classes, we see the simple string oscillator equation, which can be used to estimate the string tension at pitch for a stringed instrument. However, the equation assumes an ...
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1 vote
1 answer
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Linear wave superposition along a rope/string

This question basically roots to fundamentals of waves which is quite difficult for me to visualize. Hope that I can clear out this confusion based on answers to this question Would be grateful if ...
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1 vote
0 answers
39 views

How is tension act microscopically in a string?

Think of a massless string that goes through two pulleys attached to a roof, also massless, and look at this scenario as if you were seeing the string in its atomic constitution, looking at the parts ...
1 vote
1 answer
26 views

Will splitting a tensed string by the ends and in the middle make the two long parts not go flying around?

If you chop a guitar string with 3 swords at the exact same time: ------------ to -|-----|-----|- Would the 2 big parts not move ...
0 votes
1 answer
39 views

Balance equation for a string-spring system: meaning of 2nd Newton's law for massless objects $m=0$ [closed]

The usual homogeneous one dimensional wave equation for transverse (vertical) vibrations is given by $$u_{tt}-a^2u_{xx}=0,\qquad a=\sqrt{T/\rho}$$ where $u=u(x,t)$ is the vertical displacement, $T$ is ...
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1 vote
1 answer
141 views

Potential Energy for Non-conservative Forces

I was studying for the GRE and came across the problem below. A small puck of mass $M$ is attached to a massless string that drops through a hole in a platform, as shown in the diagram above. The ...
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2 votes
1 answer
103 views

Necessary speed for being at rest

In the figure above mass $m_1$(1.5kg) is rotating with uniform speed in a circular path of radius $r$ and mass $m_2$(2kg) is tied to $m_1$ with a thread. The coefficient of friction on the table is ...
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6 votes
2 answers
385 views

Will two bodies initially connected to and revolving around each other, start spinning when disconnected?

Two extended bodies are connected with a string and revolve around each other (that is, around the center of mass of this system). No gravity, no external forces. The string is cut, and they start to ...
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1 vote
1 answer
87 views

Application of conservation of momentum to this system has absurd implications

The system, everything shown in the picture (table, pulley, spring, string, blocks, wall), was initially at rest, with spring unstretched. Friction is absent everywhere, and spring, string, and pulley ...
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3 votes
1 answer
86 views

How to apply force due to change in momentum? [closed]

The given problem states that A rope is fastened at both ends to a ceiling, one end is allowed to fall freely. Find the maximum force that the fastening at the other end must be capable of handling. ...
1 vote
2 answers
379 views

Why is tension force in a string non-conservative?

I have this doubt for quite a while now. Suppose we have a massless inextensible string with tension as 'T', now, I would like to know that is this tension a non-conservative force? If yes, then what ...
's user avatar
3 votes
2 answers
85 views

Is the tension amplified by the number of turns made by the string? [closed]

In the following question: When I first attempted it, I considered only 1 force/Tension, which is produced directly by man on the string, because I thought that its the same force which goes around ...
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