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.
1,341 questions
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Two spools linked via a pulley: only one rotates. How to conserve energy?
I know how to get the correct answer for the following problem using dynamics, but when I approach it using the energy formulation I get the wrong answer.
Two massive, identical spools are attached to ...
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Advice for problem solving with Newton's laws of motion [closed]
I'm having trouble solving problems like this. Which actual fundamental concepts should I review again, and which types of problems should I practice again?
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Fixed vs free ends in 1D standing waves
In introductory physics courses one often discusses standing waves on a string with two fixed ends. A standard experimental demonstration of this is given here.
My problem is that in such a ...
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Will a frictionless rope in space retain its shape if all segments move tangentially with equal velocity?
Suppose we have a uniform, massive, flexible, frictionless and non-stretchable rope in space, initially shaped arbitrarily. Each infinitesimal segment of the rope is given the same velocity in the ...
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Position-independent horizontal forces in catenary chain
In deriving the differential equation for a catenary chain, one key assumption is that the magnitude of the horizontal forces is independent of time. If we look at the diagram below
(reproduced from ...
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What keeps cotton thread together and why does old cotton thread becomes easily torn apart?
One of my old t-shirts recently got a tear. When I pull near the tear, it easily tears more and more apart. When I looked through 20x magnification, I don't see difference of thread in place where it ...
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How do I make sense of the wavelength for the second harmonic?
This is probably a very elementary question, but for the second harmonic, we have $L=n\lambda/2=\lambda$.
But how does this make sense?
$\lambda$ is the distance between the two ends of the string. ...
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Why are strings in string theory considered as elementary?
I was reading "The classical theory of fields" by Landau & Lifshitz and, in the beginning of the third chapter of the 4th edition, they explain that the existence of a rigid body is ...
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Rope problem with multiple objects [closed]
I want to know in this diagram why can't I assume the rope that has angle θ1 is the hypotenuse of a right triangle and since vertical segment has tension 5N and slanted rope has same tension then why ...
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Velocites along mutually perpendicular axis can be negative to each other?
This is from a Mechanics book.
Explain the highlighted statement please. How can $v_a$ and $v_b$ be opposite in sign when both velocites are along mutually perpendicular axis?
The book is making an ...
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Acceleration in Atwood machine
Is it possible that $2$ blocks (say, $M_1$ and $M_2$) attached to a pulley with an ideal rope (inextensible) to have different acceleration in any condition?
My doubt arises from the fact that the ...
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How can a light string make a pendulum without becoming slack?
I have seen a lot of physics problems involving a bob hung using a light string from a hinge point and then we give some intial velocity $v$ in horizental direction Then its said that if $v \geq \sqrt{...
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What is the rigorous justification for using a single scalar acceleration in multi-axis Atwood systems?
In solving Atwood-type systems—especially those involving inclines or pulleys—we’re usually taught the following approach:
Choose a direction of motion (e.g., “block A moves down the incline”).
...
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Loose pulley tension and forces
I have a quick conceptual question in the construction below when there is a loose pulley holding L.
Will the tension everywhere in the string be the same so that the right and left side will have the ...
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Determining direction of motion: particle on a rough slope (mechanics)
Suppose we have the following set-up:
The inclined plane is rough and the coefficient of friction between it and mass $m$ is $\mu$.
The pulley is smooth and the string connecting the particles is ...
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Normal stress of a wire (vertically hung, supporting a weight), when its cross-sectional area isn't constant throughout the length
It's easy to calculate the normal stress of a wire—whether it’s pulled along its length or supporting a mass when hung vertically—by using the formula $\frac FA$, but only if its cross-sectional area ...
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Shape of a rope in steady flow [closed]
I want to measure flow speed in an exotic way: with a hanging inelastic rope/thread/string/chain.
Assume we have a cylindrical, flexible thread, hung from one end in a steady flow. I assume inviscid, ...
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The problem of the perfectly horizontal string
Suppose we have a piece of string, of non-zero mass, whose two ends are attached to two heavy blocks, where the two points of attachment have the same height measured from the ground.
In other words, ...
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Why does tension force exist and what is it's magnitude at various points of a large body? [closed]
I want to calculate, specifically the magnitude of tension force in various scenarios in a rigid body and understand why it's existence is even necessary.
My understanding: I do understand that ...
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Tension in a bent rope
If I bend a piece of rope into a sort of a ring (let's say I join the 2 ends in a knot), it will be under tension. Will there be a tension at all points of the rope? If so, will it be tangential at ...
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Formulating the catenary problem as a variational problem
I am interested in studying the curve a string follows when fixed by two points and subject to a (uniform) gravitational field. Say the string has a constant length $L$ and is fixed on two points A, B ...
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Hannah Fry Christmas lecture problem: mug falling on a string attached to a mass 14 times lighter
This is a problem I came across on the Royal Institution Christmas lecture 2019.
It involves a mug (i.e. a heavy mass) attached to a string that curves around a rod and then leads horizontally to a ...
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Upper bound for the lowest transverse oscillation frequency of a 2D string with non-uniform density
I'm working on Problem 4.5 from A First Course in String Theory by B. Zwiebach. The problem involves a nonrelativistic 2D string with fixed endpoints at $(x=0,y=0)$ and $(x=a,y=0)$, position-dependent ...
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Question about how $F= 2ma$ [closed]
Hello everybody, I was reviewing this study guide that my professor provided and was confused by this problem. I understand the entire process of determining acceleration, however I was confused by ...
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Determining String Tension from Tuning Peg Turns?
Follow-up Question:
Building on my previous question about the mechanism of guitar string tuning, I was wondering if it's theoretically possible to determine the tension in a guitar string simply by ...
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