Questions tagged [torque]

This tag is for questions regarding to Torque which is a measure of the force that can cause an object to rotate about an axis.

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Resolution of force sum

I was able to find resultant of forces by resolving it. I am getting problem in what we have to actually find resultant or moment of force along a particular point. Just need help that what actually ...
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3answers
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Why does a spear or a javelin turn in the air?

In videos of the javelin throw, the throwers consistently seem to grip the spear at the center of mass and launch it by imparting it an initial velocity. What causes the javelin to turn around an axis ...
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Angular momentum and momentum of a force explanation for students of an high school

This question is created to get additional information for my students from a high school. We know that the angular moment is given by: $$\mathbf{L}=\mathbf{r}\times \mathbf{p}=m(\mathbf{r}\times \...
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Steel plate suspended by threads, calculate forces

A flat, homogeneous sheet of steel with mass $m$ is suspended by rope according to the picture: I am asked to determine the forces $H,V,S$. I've come up with the force equations $$V+S\sin{45} -mg = 0$...
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Pivotal forces , $α= a/r$ & $α=τ/I$ where $α$ is angular acceleration, $a$ is tangential acceleration, $τ$ torque, $I$ Moment of inertia

When pivotal forces are present we can use α=a/r where a is net tangential acceleration but we need to know the pivot force against force of gravity (mostly) so that we will get a net value for a......
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1answer
24 views

How to determine the direction of moments (confusion)?

My teacher is showing me a few ways that I can calculate moment and its direction. In this example, she is going to use the principle of moments to solve this (ie resolving into components) But what ...
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3answers
103 views

What rotates a door, torque or force?

I am confused as to what causes a door to rotate. Assume I apply a force to the edge of the door, with the door initially at rest. Force is perpendicular to the door, so it would create a torque. But ...
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0answers
27 views

Torque in a harmonically oscillating body?

The system oscillates simple harmonically And my question is will the block exert a torque on the rod with respect to the point A? Based on my understanding, Spring 1 and spring 2 both will produce ...
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2answers
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+200

Physics of the Planche

The planche is a gymnastics exercise where the athlete holds their body parallel to ground supported only by their hands. People sometimes train for this exercise using a progression of ``planche ...
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Does a piston push harder against its wall with decreasing load force?

I'm building a force model of a piston for a robot simulation, and I've reasoned that when the piston is not moving, as the load force drops, the horizontal force into the wall seems to increase for ...
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2answers
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One piston power and force [closed]

I am trying to figure out, what does the engine power rating mean regarding to single-piston performance. A gasoline or diesel engine is rated for let's say 100kW of power at 4000 RPM. Let's assume ...
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3answers
63 views

Total forces is 0 equivalent that the torque is 0?

I came across a theorem that states that : for a solid body (made of a collection of points $M_i$ of masses $m_i$ and speed $\overrightarrow{v_i}$ ) in rotation around a point $O$ under the action ...
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0answers
60 views

Cross product and determinants [migrated]

The determinant of a $3 \times 3$ matrix gives the volume of the parallepiped formed by 3 vectors. With the cross product, say to find the torque, we find the $3 \times 3$ determinant value of ...
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Applying multiple forces in different places

Let's say we have a situation where we have two masses connected to each other (horizontal). The connection is rigid, massless, and has a constant distance, let's say 1 metre. We'll call the masses m1 ...
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1answer
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Accelerometer Vs gyroscope - measuring torque [closed]

Torque can be measured with an accelerometer (tangential-acceleration): t = Fr and F=ma, so we get a from the accelerometer, giving: t = mar Torque can also be measured with a gyroscope (angular-...
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4answers
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Toilet paper dilemma

There are two ways to orient the toilet paper: "over" (left image), "under" (right image). Each has it's pros and cons. For some reason, it's always easier to tear off the paper ...
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1answer
43 views

How to calculate the change in angle due to the righting moment of a ship?

I trying to calculate how the forces on a boat (initially out of equilibrium) work to right it. The cross section of the boat is a convex polygon and constant throughout its length. I can find the ...
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1answer
28 views

Newton's 3rd Law Coil in Magnetic Field

When a current-carrying rectangular loop is placed in a magnetic field, the forces acting on either side of the loop which is perpendicular to the field provides a torque which rotates the loop. ...
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2answers
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How do we distinguish between systems and bodies when dealing with forces and moments?

In my preperation for an exam I came across the following question: In this question I treated the hinged laders as one body and thereby resulted forces and took moments. However, this does not yield ...
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4answers
81 views

Intuitive question about torque formula

Consider two objects as shown: On one side a box with mass 1 kg, 2 m apart from pivot and on the other side two boxes of mass (1 kg each), 1 m apart from pivot, balance a seesaw. This is the question:...
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How could a motor keep a platform in position, lift it, and lower it?

A subsequent question stemming from here. Assume it is a motor supplying the torque to the pulley. When the motor only supplies enough torque to keep the platform in place, is it the stall torque ...
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1answer
50 views

What force would a cable winding onto a pulley experience?

I am quite confused about pulley problems with cable on only one side. Like how I draw here The massless and frictionless pulley in blue with rotational inertia J and radius R is fixed on a platform ...
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5answers
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Find the normal force on beam in asymmetrical scenario [closed]

A thin beam with evenly distributed mass $M$ and length $L$ is resting on two spikes as shown below. What is the vertical normal force $F_l$ on the beam exerted by the left spike? Solution The ...
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25 views

Finding torque on dipole from the force on it

The force on an electric dipole $\mathbf p$ due to field $\mathbf E$ is given by $\mathbf{F=(p\cdot\nabla)E}$. We should then be able to find the well-known torque $\mathbf{\tau=p\times E}$ by using ...
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1answer
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This is question is originally in context to elasticity (young mod, bulk mod etc). but i want some clarity on the tension forces (or torque)

I want to know what tension will there be in 2 strings if the are connected by rod and a mass is hung somewhere in between .I somewhat know the concept of torque but I am getting confused here . pls ...
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1answer
67 views

Why are there no brushless motors with more than 3 phases (6, 9, etc.)?

My understanding is that adding phases will (up to a point) add the ability to push more power through a motor (more Amps total, same per individual winding wire), generating more torque for similar ...
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0answers
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How weighing balance works and can balance itself?

i am new in this community and i was not able to answer in a similar post "how does a weighing balance that has 2 identical mass on both sides is capable of balancing after being tilted". i ...
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1answer
37 views

Pure roll condition equivalence

In this video: https://www.youtube.com/watch?v=rjz0XeK0gr0&t=315s at 5 minutes, Professor Walter Lewin says that considering the pure roll condition, having the disk rotating about its center of ...
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1answer
17 views

How do I calculate angular momentum given constant torque?

Suppose I have a wheel that is initially at rest at $t = 0$ and a constant torque $\tau$ is tangentially applied to it. I want to measure the angular momentum of the system at time $t$. Would I ...
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2answers
88 views

Why is angular momentum of object about its axis equal to that of a non-moving parallel axis?

Take for example earth. Earth has angular momentum about its own axis. However, if we ignore the orbital portion, the angular momentum of the earth relative to the sun's axis is the same. Another ...
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1answer
41 views

Calculating Angular Acceleration using Torque and Rotational Inertia [closed]

I don't understand why my approach to this problem is wrong. Two masses, one with mass $m$, and the other with mass $2m$, are attached to a light rigid rod as shown below. When the system is released ...
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1answer
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The Physics Of A TRX (or Suspension Trainer) Row - How Much Am I Lifting?

I'm not sure how to solve this problem. It looks like a sum of torque moments issue on one level, much like a push up. But with the push up, for the most part I'm only dealing with vertical components....
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0answers
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Torque on rod caused by torque on ring

Consider the following arrangement where a rod is hung by two strings from a ceiling: A charged ring rotates about its center with an angular velocity $\omega$. There is a uniform magnetic field ...
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25 views

How to calculate the total torque for a rod whose axis of rotation keeps changing due to external force

Suppose I have a rod of length L and mass M. I swing the rod by holding at one end. I need to compute the total torque acting on the rod if I know the position of the center of mass of the rod and the ...
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1answer
38 views

Is there any fundamental relationship between the torque on a classical magnetic moment due to a field, and the Lorentz force on a moving charge?

I was studying recently and noticed that the torque on a magnetic moment due to a field is defined as $\tau = \mu \times B$. Classically, as far as I'm aware, the magnetic moment is given by $\gamma L$...
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2answers
36 views

Torque experienced by a body under shearing stress

Given below is a piece of information from table 9.4 on page 243 from my standard NCERT class 11th textbook: Two equal and opposite forces parallel to opposite surfaces forces in each case such that ...
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2answers
412 views

Why do we neglect torque caused by tension of curved part of rope in massive pulleys?

In this MIT OCW lecture, the professor analyzes a block - massive pulley - block system as shown here: The analysis was easy enough to follow till this point: Here he says the only the end points of ...
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1answer
50 views

How is the “wrench” a simplification for a general force-couple system? [closed]

from engineering mechanics, by beer and johnston For any system of n forces, we can simplify this system to a Force-Couple system. The simplification is intuitive- we don't need lot of forces just a ...
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1answer
83 views

Finding relation between Torque and rate of change of Angular momentum , different approaches are giving different results [closed]

All the vectors here are measured in the inertial frame of reference $I$ . Notation used : $O$(origin) is a fixed point in $I$ . $C$ is the center of mass of the rigid body that I am considering and $...
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3answers
42 views

Are translational KE and rotational KE exactly analogous?

My textbook states that translational KE and rotational KE are completely analogous. The author states "They both are the energy of motion involved with the coordinated(non random) movement of ...
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0answers
18 views

What do bending moments look like after coordinate frame rotation?

Suppose a 3D body had certain bending moments about the x, y, and z axes. What would the bending moments about a different coordinate system look like? In my case, I have restricted myself to a planar ...
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1answer
44 views

Precessional motion of a spinning top

In Feynman's book, when he talks about the motion of a rapidly spinning top, he mentions: "When we apply a Torque to a rapidly spinning top, the direction of the precessional motion is in the ...
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0answers
15 views

Moment on a rectangular concrete slab

Here is a picture from my engineering textbook. It describes a concrete slab being subjected to normal force $P$ and a certain moment. The moment is expressed by the normal load $P$ affecting at some ...
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1answer
35 views

Finding the maximum force acting on a rolling tire

I have a problem where a lone tire is rolling, we may assume that the tire is a uniform disk. I need to find the maximum force acting on the tire as a function of friction if the tire rolls without ...
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1answer
68 views

Which force exerted a torque?

Suppose a horizontal disc fixed in the center with a vertical shaft passing perpendicular to the plane, is rotating at some angular speed and there is an insect sitting initially at center. The insect ...
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2answers
55 views

Non-conservation of angular momentum example but is an external torque really required?

Say a man is twisting his body using internal body muscle contractions and torque interactions between his feet and ground (no slipping). From the answers of a previous question I raised, these ground ...
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1answer
19 views

Average torque on a Projectile of mass $m$ with initial speed $u$ and angle of projection $θ$ between initial ($P$) and final ($Q$) positions is [closed]

Question is as follows: Average torque on a Projectile of mass $m$ with initial speed $u$ and angle of projection $θ$ between initial $(P)$ and final $(Q)$ positions is I researched a lot but wherever ...
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1answer
33 views

Energy conservation equation for an object rolling up an incline

An sphere of radius $R$ rolls up an incline. We can write mechanical energy conservation equations for this motion because neither does the normal or the frictional force do any work. At the top of ...
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3answers
48 views

Definition of torque in the (possibly accelerating) centre of mass frame

My lecture note states that the torque in the centre of mass frame ($O^*$) of a rigid body is: $$\bf{G^*}=\sum \bf{r^* \times F}$$ where $\bf{F}$ denotes the real force that is producing the torque ...
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2answers
93 views

In rotational motion, why $a = rα$?

The formula of torque is given by $$τ= F*r = Iα,$$ while solving some questions I came across a question of rotating pulley where these two formulas were equated to find value of $α$. How $a=rα$? a ...

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