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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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1answer
53 views

Why is the phase velocity of waves on a rope independent of the wave length?

A rope is described by the wave equation $$ (\partial_t^2 - \partial_x^2) \, \varphi = 0 $$ It is well known that there is no dispersion for resulting wave solutions. This implies that all plane waves ...
3
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3answers
698 views

Is tension always the same as centripetal force?

For example, if a ball is attached to a string and released from a vertical height and then pivots around a point to initiate circular motion, tension is equal to centripetal motion. If, on the other ...
3
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2answers
39 views

What is the difference in the way a single rope and a double rope would behave under dynamic load?

Suppose I have a single rope attached to a fixed point via a load cell, which gives a number (in kN) based on the load it's experiencing. I take a weight (x) and attach it to the rope at a fixed point ...
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0answers
21 views

Virtual Work and Arbitrary unit vectors

I was recently watching a lecture on MIT OCW where they were talking about Newton's Laws for a pulley system. The professor solved a problem pretty quickly using a method called virtual work. I tried ...
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1answer
20 views

How many ways can one possibly spin an object at the end of a string?

I had a job that required me to carry a set of keys attached to a chain for most of the summer. I found that I could spin my keys at the end of their chain in two ways: in a circle, and in a figure-8. ...
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2answers
46 views

Frames of reference in a pulley system

This question comes from the following website: https://i-want-to-study-engineering.org/q/pulley_dynamics_1/ A system consists of three light pulleys and light inextensible strings as shown ...
4
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4answers
245 views

Why does the phase velocity of a string attached to springs depend on the wave length?

A string can be described by the wave equation $$ (\partial_t^2 - \partial_x^2) \, \varphi = 0 $$ while a string attached to a spring (i.e. with a harmonic restoring force) at each location is ...
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2answers
27 views

Tension within a hypothetical pulley system

The following hypothetical pulley system exists: A massless rope passes over a frictionless pulley. Particles of mass M and M+m are suspended from the two differents ends of the rope. If m=0, the ...
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0answers
8 views

Derivation of driven force on a string. How to prove maximum amplitud is achieved at resonant frequency?

I know if I have a driven oscillator of natural frequency $\omega$, applying a driven force $F_0 \cos (\Omega t)$ will result in a motion equation like this one (steady state/particular solution): \...
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2answers
30 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 ...
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2answers
37 views

Why is the force not included?

I'm reading my physics book trying to understand how to create force equations. (This next test is going to be a flop.) In this example, it states that if we were trying to find the tension in the ...
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1answer
66 views

Do string instruments really create standing waves or not?

I have seen similar questions regarding this but containing answers that somewhat disagree with each other which makes it hard for me to understand this. My question is mainly about when plucking a ...
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0answers
14 views

Establishing separate datums

In the following question, how are we allowed to define two different zero potential energy reference points?
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2answers
80 views

Derivation of wave equation

I learned that the wave equation derivation is below. Suppose $q$ is the displacement on $y$ component, $T$ is string tension, $d$ is the interval of two particles in $x$ direction. Equation of ...
1
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1answer
42 views

Tension force on a rope question (calculate acceleration of the mass after the rope is cut) [closed]

This question is from a mock exam paper and I feel like my brain is going to explode since I've been trying to solve it since yesterday. I've been stuck on part b, I know I need to use Newton's 2nd ...
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1answer
48 views

What is the acceleration of the large block? [closed]

The answer was given mg/(2M+m). I found this one and cannot find where i made the mistake....
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3answers
4k views

Can an object tethered to a spaceship be pulled out of event horizon? [duplicate]

An object cannot escape the event horizon by catapulting it outside the black hole. However, what if instead of relying on escape velocity, the object was tethered to a ship orbiting well outside the ...
3
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1answer
58 views

Is there a relationship between the frequency of a standing wave on an oscillating string and the half-life of its amplitude as it decays?

I'm asking in the context of an experimental exercise where we used a speaker to create a standing wave on a string with constant tension, then turned off the speaker and allowed the amplitudes to ...
3
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2answers
193 views

Why can't I choose blocks attached with pulley B as a system?

Three blocks of masses m1, m2 and m3 are connected as shown in the figure. All the surfaces are frictionless and the string and pulleys are light. Find the acceleration of the block of mass m1. ...
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5answers
150 views

Wave Equation derivation

I'm curious about part of the derivation of the wave equation as is done in all references that I've seen so far (I'm gonna reproduce only the part that's puzzling me). We apply Newton's second law ...
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0answers
51 views

For wave functions $y(x, t)$, how the second order partial differentiation works as second order absolute differentiation?

Ref: http://www.animations.physics.unsw.edu.au/jw/wave_equation_speed.htm As far as we've defined wave as the disturbance caused due to Force obeying Hooke's Law. So, the derivation was started with ...
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2answers
43 views

Force and tension in a pulley

So imagine a pulley (frictionless) with a massless string. On each side are 2 weights 1 of 10 g and 1 of 20g. In the free body force diagrams for the 2nd body we say that $m(g+a)= t$ But shouldn't ...
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1answer
31 views

Newton's laws of motion tension

I am very much confused about tension. I have even Googled my doubts (Also used khan academy) to clear my doubts but even there explanation couldn't satisfy me. PLEASE SOLVE THIS QUERY:- what ...
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0answers
26 views

Wave equation, Closed string and string shooter

I have some question about wave equation in "pathological" condition. 1) what is the solution on the wave equation if the string in closed? (ex. a closed string in rotation around his center) I ...
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1answer
43 views

About working of tension force

From the past 3-4 days I have been continuously thinking how tension actually works on atomic level. I have even Googled it many times but I was not satisfied with the answers. Can anyone please help ...
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1answer
51 views

Length of Rope in Tug Of War Matter?

I had a question about Tug of War Game, Does the length of the rope really matter, whats the difference between a 50cm rope and a 5meter Rope in Force, Torque And Safety in Tug Of War.
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3answers
42 views

Tension in a string attached to different masses

Does tension in a string remain same even if masses attached to it are of different weights? I have provided a diagram, according to me the tension in string should be different as masses hanging ...
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1answer
27 views

Tension about disk

A uniform disk of mass $M = 8.0 \;\mathrm{kg}$ can rotate without friction on a fixed axis. A string is wrapped around its circumference and is attached to a $m = 6.0 \;\mathrm{kg}$ mass. The string ...
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0answers
47 views

If a string had mass in an Atwood machine, would the objects be at rest?

So I understand that the tension produced by a string in an Atwood Machine is constant throughout the string assuming it is ideal, but what if it wasn't? Wouldn't there be a tension gradient, in which ...
1
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1answer
35 views

Why pulley systems give mechanical advantage?

In a system with 2 pulleys, to lift a x kg object y meters I would need half the force that the object exerts due to gravity but pull the rope double the distance, why does this happen this way?
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1answer
48 views

Tension constraint

I have a question about the pulley configuration in the following problem: Why can't we apply the tension constraint $$T_{1a}-T_{2a}-T_{1a}=0?$$ This would imply that $T_{2a}=0$. I know this is ...
12
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6answers
685 views

When a ball on a rope swings in a circle, is there both centripetal force and tension force?

I'm learning about centripetal force and I was shown a scenario where a man was spinning a rope attached to a ball over his head. There's a centripetal acceleration toward the center and therefore a ...
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1answer
45 views

Can you please explain the statement in the David Morin's Classical Mechanics? [duplicate]

For example, in a hanging massless rope, or in a massless rope hanging over a frictionless pulley, the tension must be the same at all points, because otherwise there would be a net force on at ...
0
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1answer
38 views

Tangential Motion of an Object Attached by a Radial Elastic String [closed]

A toy car travels in a horizontal circle of radius 2a, kept on track by a radial elastic string of unstretched length a. The period of rotation is T. When the car is speeded up the string stretches ...
2
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2answers
66 views

What length can a metal wire (cable) hang vertically?

What length can a cable hang vertically with no additional weight attached to it. I tried figuring this out with 5/8 aircraft cable specs by dividing the rated weight capacity of the cable by the ...
1
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0answers
49 views

Constrained Motion [closed]

There are two bodies viz. A and B which are placed on a horizontal surface. The free end P is being pulled by a constant force of 1 N. Find the acceleration of free end P? My approach Sign ...
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1answer
67 views

Tension in a string with unequal forces

Let's suppose that there is a massless string. If we apply unequal forces along the rope along a straight line, let's say we apply 60N and 70N forces, then what is the tension in the rope? It would ...
23
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8answers
1k views

Shape of a rotating rope with one free-end [closed]

One end of a uniform rope (with total mass $M$) is fixed on the edge of a cylinder. The cylinder has a radius $R$ and rotates with angular velocity $\omega$. The axis is vertical in a gravitational ...
-1
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1answer
47 views

Newtonian Mechanics - Pulley block system, finding acceleration [closed]

The question is to find acceleration of the block m1 in the above system (please look at diagram). So I took tension along String 2 to be T and thus Tension along String 1 would be 2T. Acceleration ...
0
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1answer
55 views

Frequency of longitudinal waves on a string

I recently heard the composer Ellen Fullman on her Long String Instrument, which consists of steel wires of approx. 20 m length played by rubbing/stroking the string longitudinally. Changing the ...
1
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1answer
67 views

Tension in a string moving in elevator

A lift can move in $x$ axis and also in $y$ axis. A bob of mass m is suspended with inextensible thread inside the ceiling of elevator. Determine tension $T$ in the string when elevator moves in $x$ ...
0
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0answers
28 views

At what rate is tension released from a plucked string (eg. guitar string)?

Tension in a plucked string (such as a guitar) dictates many of the important changes that occur in the sound of the string over time. eg. It causes a pitch bend, a change in inharmonicity, and ...
1
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0answers
18 views

What is the resultant force acting upward on the point of contact under an elastic deformation?

The situation here is you have an elastic string (or a rubber band) fixed at two ends A and B. A•-------------------------------------------------•B An object is ...
2
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0answers
24 views

String conservation with springs

I was trying to solve this Problem that asked to find the period of small oscillations for this system. To do so I used the fact that for a massless pulley with strings around it, the sum of the ...
0
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1answer
36 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
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1answer
55 views

Dropping a rope in a black hole [duplicate]

If there is a spaceship hovering above a black hole so that it can get away, what would happen if the spaceship connected a rope to itself and dropped the rope in? Could you pull the rope out?
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4answers
64 views

Tension in string due to two opposite forces [duplicate]

If you attach a ideal string to a wall and pull it with force F, there should be a tension T=F in the string. And the string will apply force F on the wall too. But what if there are two persons ...
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1answer
50 views

How does velocity being given to the bob here create tension in the string? [closed]

Based on intuition, the lesser the velocity the bob is initially given, the sooner will the string slack. I don’t understand how the velocity the bob is given initially is related to tension being ...
-1
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4answers
96 views

Newtonian mechanics. If I'm inside a wagon and I pull a spring connected to the wall, will the wagon move? [closed]

Suppose the mass of the wagon is very small. There's a spring connected to the wall inside the wagon. If I pull the spring, does the wagon move?
2
votes
1answer
330 views

Friction in pulleys

The moment equation of a pulley with a rope applying tension on both sides is as follows: $$I\alpha = f + T_1R - T_2R$$ ( $I$ - moment of inertia; $\alpha$ - angular acceleration; $f$ - friction ...