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39 views

Hard problem of pulleys [closed]

A string passes over a frictionless, massless pulley attached to the ceiling A mass $m_1$ hangs from one end of this string, and a second massless, frictionless pulley hangs from the other end. A ...
1 vote
0 answers
24 views

What is the friction coefficient of Object 1 and table top? [closed]

Assume one box with a mass of 1 kg and acceleration of 5.41m/s² to the left. And another box mass of 2kg is hanging on a pulley with a weightless rope. What is the friction coefficient of Object 1 and ...
1 vote
0 answers
32 views

Does normal force always point perpendicular to the surface? [closed]

I drew arrow #2 on an AP Physics C assignment, but my teacher said it was wrong and took away a point since it was not perfectly vertical. I feel like it could be arrow #2 though with the information ...
1 vote
0 answers
13 views

String taut condition in a Vertical Circular Motion [closed]

Suppose, a ball is tied to a massless string attached to fixed point. In the initial condition, it hangs freely along the vertical in the influence of gravity. Now it is given an initial velocity u in ...
1 vote
1 answer
38 views

Velocity and Acceleration in an Accelerated Atwood Machine

Suppose an ideal Atwood machine is pulled by a constant force $F$ against gravity. I am unable to understand the dynamics of the system. Do the blocks move in such a way that the "increase" ...
1 vote
2 answers
47 views

Confusion about tensions and friction in pulley problem

The pulley is not massless, and has moment of inertia about the hinge point $I$. We assume there is no slipping of the rope. My teacher said that the first equation we make will be $T_1 = f + T_2$ or $...
  • 279
0 votes
3 answers
70 views

Angle of Conical Pendulum

Setup A ball of mass $m$ is attached to a string of length $L$. It is made to rotate at speed $\omega$ as a conical pendulum making an angle $\theta$ with the vertical. Question This post shows how ...
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0 votes
1 answer
25 views

Why is the Horizontal Tension same here?

Our sir told us that the horizontal tension will be equal throughout the string but why
-1 votes
1 answer
32 views

What forces act on the block? [closed]

I can not understand why the forces N1 and N2 act on the block. What are these forces and why did they appear?
0 votes
1 answer
39 views

Can We Have 0 Normal Between Any Two Bodies Just Touching Each Other

I am a bit confused... Here if we see x-axis forces they are getting detached from each other. So To Resist them The Normal Should Be Zero. I am not sure if I am applying the right logic or not but ...
0 votes
2 answers
56 views

How To Find Direction of Normal Contact Force?

I am a little bit confused. while doing questions I can see direction of normal forces are different. In Some Cases, It is perpendicular to the contact surface and towards the object on which normal ...
5 votes
3 answers
1k views

Where would a string break if an instantaneous UNEQUAL tensile force is applied on the ends?

Similar to a question asked previously except this time with unequal tensile forces at the ends: Where would a string being pulled from both sides snap and why? Assume the string is homogenous. Would ...
-1 votes
2 answers
48 views

Does (supporting) rope tension at angles below 45 degrees, increase under load & how?

A (semi) cantilevered object such as a door canopy / porch bolted to the face / lintel area of a wall, often requires rod/rope support at the free end. The "lightweight" supporting rope or ...
1 vote
1 answer
40 views

What is the correct friction coefficient and theta (capstan equation) for a strap/rope in a tie down mechanism?

I am curious about the mechanism of the tie-down strap. I understand that these devices typically will use a ratchet-prawl mechanism to incrementally wrap a (typically polymer based) strap around ...
1 vote
1 answer
73 views

Is there a difference between 10kg weight exerting 98N force vs. a person pulling the string with 98N force? [closed]

My question is related to an AP Physics question (2.k acceleration of systems), which appears simple, but the premise of part 2 of the question is difficult to understand, hence asking the physics ...
0 votes
0 answers
16 views

Tension in a string and external force [duplicate]

If an external force is applied on an ideal string (in a pulley system) then does that external force become the tension throughout the string?
0 votes
2 answers
102 views

Tension in a massless rope [closed]

I have been really confused on the rxn pair of tension by a massless string on a an object or a man. (PLEASE NOTE THAT:-the 1,2,3 numbers i use in this question actually represent the parts of string ...
0 votes
4 answers
78 views

Body moves in circular motion

If a body moves in circular motion like: a ball attached to a rope or a charge moves in circular motion due to magnetic field My question is as follows: Why the rotating force doesn't create a ...
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1 vote
0 answers
23 views

Find the acceleration of blocks in the elevator [closed]

How to find the acceleration of each block when elevator is accelerating upwards.
1 vote
1 answer
61 views

Tension in moving chain [closed]

Suppose I have a chain in equilibrium position (a catenary). The only force acting on it is gravity. Now, say that I move this chain in such a way that every point traces this catenary. Basically, the ...
8 votes
2 answers
203 views

The classic falling rope problem

A rope was on top of a table with a part of it hanging off the edge, without any friction. The equation of the motion is: \begin{equation} \frac{mgx}{L}=m \frac{dx^2}{dt^2} \to \ddot{x}=\frac{gx}{L} \...
2 votes
1 answer
84 views

Understanding coordinate system for looping pendulum equations of motion

I'm interested in the phenomenon of the looping pendulum, which is a system consisting of one large and one small mass connected by a string passing over a rod. In particular, I've been looking at ...
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0 votes
3 answers
46 views

Uniform Vertical Circular motion

I've been studying physics recently particularly the uniform circular motion topic. I have read about an example that an object attached to a string moving in a vertical circular path is not a uniform ...
  • 3
2 votes
2 answers
574 views

An object is being swung around in a circle, attached by a string. If the string breaks, does the angular velocity instantly drop to zero?

If an object attached to a string is being swung around in a circle, then when the string breaks, the object will continue in a straight line at a constant velocity, per Newton's First Law. If I ...
  • 303
0 votes
1 answer
53 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 ...
0 votes
0 answers
36 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
0 answers
23 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 ...
2 votes
5 answers
654 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 ...
1 vote
2 answers
49 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 ...
  • 163
0 votes
1 answer
184 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 ...
2 votes
0 answers
138 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 ...
  • 292
1 vote
1 answer
87 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 ...
  • 897
1 vote
1 answer
94 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 ...
0 votes
3 answers
104 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 ...
1 vote
3 answers
169 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 ...
  • 897
0 votes
2 answers
89 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 ...
0 votes
1 answer
52 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 ...
0 votes
2 answers
45 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 ...
7 votes
3 answers
627 views

Is it really the Tension in the rope that pulls the pulley?

We always solve questions by drawing two tension forces at the diametrically opposite end, to show that tension is pulling the pulley, but from the research I have done, it is clear that it is not ...
-1 votes
1 answer
57 views

Falling stones attached by a string

Suppose we have two stones, one "big" (A) and one "small" (B), the smaller one over the big one at the moment of free fall. Suppose also that a string of a certain length is ...
1 vote
2 answers
77 views

How do I find the constraint relation in this question?

Let $\alpha_1$ and $\alpha_2$ be the angular acceleration of top pulley and bottom pulley respectively while $a$ is the acceleration of centre of mass of bottom pulley. Then, $$\alpha_2r+a=\alpha_1r$$ ...
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0 votes
1 answer
35 views

Elemental problem of dynamics

Ok, let's go fast. If we have the following system, and we want it to be static (acceleration = 0), we will always and obligatorily need friction, or any other force to oppose those existing in the ...
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0 votes
1 answer
43 views

How do i calculate the tension in string here? [closed]

How do I calculate the tension of string? I have already calculated the acceleration of the 2 masses which is 3m/s. But I can't seem to arrive at the answer which is 9.00N. Sorry if this was a ...
2 votes
1 answer
41 views

Determine which ropes are under tension in pulley systems

These questions is gotten from beer and Johnston vector mechanics, the solution manual reveals: i) the two portions ropes are under tension in (a) - this I understand ii) only two out of the three ...
0 votes
1 answer
49 views

Tension in thread

We know a thread or string experiences the same tension force throughout the whole length,but when we tie a knot in the thread,why does the tension force become different in the two sides of the knot? ...
  • 897
0 votes
1 answer
48 views

Can tension change in a massless string if there are three forces acting on it?

Consider this massless string, which has three forces acting on it, two on the ends and one at the middle: Would the tension change at the midpoint where the $5 \text{N}$ force is applied? I think it ...
  • 313
0 votes
1 answer
117 views

What does it really mean to have infinite tension?

Let an object of mass $m$ lie on a wire. The wire is much smaller in mass than the object and so its mass can be negligible. As the object lies on the wire, the wire is pulled down to a position where ...
1 vote
2 answers
94 views

Why does a pulley rotates?

I have beening dealing with problems involving pulleys. It seems like a pulley is something that changes the direction of a string, and it rotates when the string moves on it. Why do we need something ...
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1 vote
4 answers
93 views

Confusion about tension and disk

Why are the two tensions not equal? I thought tensions on two ends of a cord are always equal. And are the motion of the disk caused by friction force due to the motion of the cord and disk surfaces?
  • 207
1 vote
0 answers
24 views

How to find accelerations/tensions here? [duplicate]

$m_{2} = 6 m$, $m_{1} = m$, $m_{3} = 3 m$ I used conservation of string length and got $a_{3} + a_{pulley} + a_{1} = a_{2}$ and $T_{1} = 2 T_{2}$, but I have a feeling it's wrong because if the pulley ...
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