# 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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### Exceeding speed of light in simple mechanical setup

Suppose a system as shown. If i pull block $m1$ and $m2$ (the two side masses) with speed $v$ and theta is the angle mentioned the speed of central block becomes vsectheta in vertical direction. If ...
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### A paradox to law of conservation of angular momentum

I came across the following problem: A small body of mass $M$ tied to a non stretchable string moves over a smooth horizontal plane. The other end is being drawn into a hole with constant speed. Find ...
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### How does the net vertical force equation for a non-relativistic string derived?

In the following image from "A first course in string theory", we get the net vertical force of a string, dFv. While I understand the first equation, I don't understand how the second ...
1 vote
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### How does the work done by a cord-over-a-pulley work? [closed]

I can use the integral of power with respect to time to solve problem. In this situation, what is the work done on the cart by the tension? Please do not use calculus.
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1 vote
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### What is the constraint acceleration equation of the system? [closed]

In the question there is a hint given, $y_A$ is not constant. From this hint I began to look at the pulley that holds $m_1$ and $m_2$, and can see that it has the same tension as $m_3$. From this ...
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### What is the centripetal force when a bar rotates about its center of mass?

Scenario 1: The centripetal force acting on the ball towards the center of rotation is $\frac{mv^2}{r}$, where $m =$ mass of the ball, $v =$ magnitude of the instantaneous linear velocity of the ball,...
1 vote
78 views

### Sound of string in a guitar

I study about waves and I learn that the velocity of a transverse wave in a string depends only on the tension and the density of the string. The frequency depends only on the source (whatever ...
• 21
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### Why is the acceleration of $m_2$ downward?

The magnitude of the acceleration of $m_2$ is $a$. It does not say in the question whether it is downward or upward. But the answer assumes it is downward. So I think either it is badly framed, or it ...
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749 views

### What physical state of a wound string corresponds to a 'tuned' string?

Many instruments can be strung with strings comprised of a solid core and wound with another metal wire, e.g. the viola. I was wondering about the physical state of wound strings when they are 'in ...
175 views

### What is Tension in a string? How is it produced at a molecular level?

I can't understand the direction of tension. Why is the direction of tension at the ends of a string away from the object or block of mass? Can someone tell me what happens internally in a string? ps: ...
1 vote
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### What is the difference between these two falling rope motion?

Here are two falling rope problems in Marion's Classical Dynamics Textbook and both equations of motion given by manual solution. (There is a typo in the third line of solution 9.15, one of the terms ...
49 views

### Work of the tension acting as the centripetal force in a circular motion of varying radius

Consider this arrangement: A point mass (its mass being $m$) is executing uniform circular motion on a frictionless horizontal plane. A string passing through the center of the circle and attached to ...
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### When to use positive and negative $\rm g$ when calculating force?

My teacher gave us a question the other day: A $20\ \rm kg$ sign is supposed to hang from a pair of wires attached to the wall and support beam as shown in the diagram. The worded that will be used ...
32 views

### Motion of non-homogeneous string fixed at both ends when pulled at a point

How to solve displacement and velocity profile of string which has density $d_{1}$ till distance $x$ and density $d_{2}$ from $l - x$ to $x$ fixed at both ends and when given initial displacement and ...
84 views

### Determining the equations of motion for a 2 DOF in 2 directions

I'm having trouble understanding a 2DOF system that moves in 2 directions. The problem asks me to determine the EOM for a system shown in the attached image: My first idea is to transform this system ...
1 vote
31 views

### Constraint rate change problem [closed]

Two small rings O and O' are put on two vertical stationary rods AB and A'B' , respectively. One end of the inextensible threads tied at point A'. The thread passes through ring O' and it's other end ...
58 views

### What happens when I grab a rope after jumping down?

If a body has a mass of 54 kg and falls straight down for 11.33m before grabbing a rope, what are the forces acting here? What part does the coefficient of friction between the rope and hand play?
40 views

### When the tensile force is equal to the weight of the body

I have met a lot of problems where the tensile force is different from $mg$, while in this one problem in the solutions it is written only that the tensile force is equal to mg. So if someone has time ...
41 views

### Why while solving some specific problems like this we need the second-order variation like this one?

Consider a string which is fixed at both ends and we are giving it a small amplitude by tauting it and moving to and from. If someone wants to derive the wave equation of the string, they would first ...
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1 vote
174 views

### What is positive rotation direction of a pulley in the Atwood machine?

In the Atwood machine the mass $m_1$ hangs on the left and $m_2$ hangs on the right, with $m_2 > m_1$. When released from rest the system accelerates clockwise which we define to be the positive ...
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113 views

### What exactly happens, step by step, in string harmonics?

I know that a string when plucked shows harmonics but I do not really understand how. Like, I understand resonating air column and how standing waves are formed there, but I can't seem to get the step ...
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### Why does plucking a string produce harmonics instead of a pulse?

If I jerk a wire from the free end fixed at an end and then fix the free end, it will produce a pulse travelling back and forth between the two ends. So in a string fixed at both ends, if we pluck it ...
• 1,086
41 views

### Why do we feel weightless while free fall but not while hanging with a string?

So why do we feel weighted by hanging on a string as their is no normal force acting on the object only tension force on the string not on object
53 views

### Angular Momentum Conservation..04

A stone is attached to a string and is revolved in a circular path with constant angular velocity $\Omega$. In this state its angular momentum is $L$. If the length of the string is reduced to half ...
42 views

### What the reason for not taking contribution of gravity when a wave is propagating?

Suppose a wave is being transmitted from one end of rope to other , for small amplitudes the wave speed is √T/u , suppose now that amplitudes of wave are not small and that gravity is also need to be ...
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### Question about the modulus of elasticity of a half-string

Question The ends of a light elastic string of natural length 0.8m and modulus of elasticity $\lambda$ N are attached to fixed points A and B which are 1.2m apart at the same horizontal level. A ...
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### Taut strings in curved spacetime

In general relativity, a straight line is defined (or, in a sense, replaced?) by the path a light beam takes. In Newtonian physics, another way to approximate a straight line between two points is to ...
42 views

### Determining moment and accelerations of blocks connected through rope and pulley [closed]

A pulley, of radius $r$, mass $m$ and moment of inertia $I$ with respect to the axis orthogonal to the vertical plane where the pulley is positioned and going through its center, two masses are ...
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1 vote
75 views

### Standing wave in a string clamped at one end

*In the case of a standing wave formed with one end clamped (fixed), there is an anti-node at the free end irrespective of the overtone. My question is why is there has to be an antinode. Is there any ...
32 views

### How do (if) the relative paces of time differ in these circular motions?

I) Imagine two equal masses tied tethered together by a rope in empty space. The rotate around their COM in the middle of the rope. The masses don't cause gravity. The masses don't move wrt one ...
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### Slackening of string in vertical circular motion

My physics teacher says that in vertical circular motion of a mass $m$ connected to a string, the tension in the string will become $0$ (i.e. the string slacks) when the radial component of the force ...
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### How does a rope's tension work?

A problem I encountered is as follows: A pulley consists of a circle of radius $R$ is pivoted about a point a distance $R/2$ from the circle’s center. A string attaches to a block hanging from the ...
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44 views

### Force acting on two wires due to a rod

Here a rod of mass $M$ is hung with the help of two cylindrical wires marked with yellow and red colors. We know the weight of the rod is acting on the center of gravity of the rod(mid point of the ...
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### Static equilibrium | A beam is hanging by two ropes with angles and there is a block on it [closed]

I have this problem model and I'm trying to get the solved equations for the distance $d$ and the tension $\vec{T_2}$ with the known values of angles $\alpha$ and $\theta$, $\vec{P_1}$, $\vec{P_2}$ ...
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1 vote
46 views

### Freely Moving Cloth Clip on a String

A cloth clip is kept on a rope such that it can move freely along the rope. The rope is slack, (but tied at two end such that the clip cannot escape), is rotated at a high speed for a substantial time ...
1 vote