Questions tagged [torque]

The tendency of a force to rotate an object about an arbitrary axis.

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Using Side Thruster on a missile to create an angular accelration

Assume a rocket is standing on the ground with mass = 1000 kg, and near the top of rocket we apply a force of 100 N for say 1 sec,now assume that this is sufficient to tip rocket over/start tipping ...
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Why is the angular momentum defined as the cross product of linear momentum and the radius?

I first searched why is Torque defined as a cross product and a lot of people answered that it is defined as a cross product because angular momentum is defined that way and it is only logical that ...
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Are force vectors members of a vector space?

Vectors in vector spaces depend only on their size and direction. Force vectors, for example, depend also on their location. Opposite force at different locations, for example, do not annihilate each ...
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Why the cross product of two vectors gives a vector in an orthogonal direction? [duplicate]

I understood the concept of cross product with an example of Torque. I understood the concept. But what confuses me is that how can cross product of two orthogonal vector in a plane give us the ...
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Why only perpendicular or parallel forces are counted? [closed]

Usually in physics, we take components of a vector (let's say force) to find the answer. Eg:- while finding force to calculate torque we find Fsin(theta) There are numerous such examples where we ...
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Why does the net torque not turn this object? [closed]

Here the object does not spin on the surface. (point $O$ has $M_o = 0$) However, there are non-zero net torques on the object at points $A$ and $B$ ($M_a$, $M_b \neq 0$). Why do these net torques not ...
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How to calculate the full load speed of a motor given the terminal voltage, armature resistance, armature current and torque? [closed]

I'm currently working on an assignment question as shown: A 220V dc motor has an armature resistance of 0.5 Ω. The full load armature current is 20 A. The starting torque of the motor is 880 N‐m, ...
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1answer
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Is magnitude of cross product commutative?

By definition of magnitude of cross product: $\| \mathbf{F} \times \mathbf{r} \|= \| \mathbf{F} \|\ \| \mathbf{r} \| \sin (\mathbf{F},\mathbf{r}) \tag1$ $\| \mathbf{r} \times \mathbf{F} \|= \| \...
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Why is the gravitational force that is measured not doubled in the Cavendish experiment?

Each of the smaller spheres is attracted by one bigger sphere. The rotation would work even if just one of the smaller spheres were attracted by a bigger sphere. What is the difference between these ...
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1answer
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Coulomb torsion balance : force or torque

The following links talk about the torsion balance equation of Coulomb. $$F_{\tau} = w \dfrac{\alpha\ D^4}{l}$$ Due to a wide variety of names for the $LHS$ of equation, I am totally confused ...
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Force couple off centre of mass in space [closed]

This object is in space with it's centre of mass at point O. I can't understand how the object will react and rotate due to the force couple. In my mind i picture the object rotating around the ...
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Derivative of angular momentum in a rotating frame of reference

I keep seeing that when taking the time derivative of the angular momentum in a rotating reference frame, we get: $$\frac{d\vec{L}}{dt} = \vec{\tau} + \vec{\omega} \times \vec{L}$$ meaning the torque ...
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Point of application of pseudo-force?

Why do we take pseudo-force to pass through center of mass of a rigid body while calculating torque on the body using a non-inertial frame of reference? I was just told this fact in my class and ...
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1answer
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Can $T = R \times F$ be used in rolling with slipping?

There is a solid cylinder rolling with slipping down an inclined plane. I am trying to find $\alpha$ (i.e. the angular acceleration) using the relation $\tau = I \alpha$. I know the value of $R$, $F_{...
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In Rotational Dynamics do we have to consider the torque of pseudo force in Instantaneous Axis of Rotation frame? [closed]

In the attached image have I done everything right? If yes then why there is no torque of Pseudo Force?
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5answers
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Center of mass of constrained rigid body

Say we have a rod with center of mass at its geometric center. Rigid bodies rotate around center of mass. If you apply force $\mathbf{F}$ at distance $\mathbf{r}$ from center of mass you generate ...
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1answer
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Apply a force to a rotating wheel

Consider a wheel with the center point O of the wheel is fixed and rotating freely around an axis passing through O. Assume that it is spinning in the horizontal plane and that there is no force ...
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1answer
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Torque cross product

Torque is the cross product of force and distance. Almost all the resources I find online have the formula as $\vec\tau=\vec d\times \vec F$, yet my professor (and I've seen some other sources do ...
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Rolling wheel precession

I wanted to write the equations of the motion of a tilted spinning wheel. I am aware of the effects of precession on spinning things, and I know the equations for the case where the pivot point of the ...
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2answers
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A problem about moment (torque ) [closed]

Everybody knows that moment of a force increases with distance. However, there is a problem about it that makes me confused these days: Let's take a look at this picture due to the formula M = F.d, ...
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3answers
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Why is the torque exerted by the magnetic field in a moving coil galvanometer independent of the angle of rotation?

How does an iron core cause the magnetic field to be constant and always perpendicular to the loop's moment in a galvanometer? The following image is from my textbook: Image source: NCERT Physics ...
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1answer
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Acceleration of a sphere with cavity in the incline [closed]

Does the object in the figure above undergo an uniformly accelerated motion? (Let's assume that the object rolls without slipping, ignore $\theta$) I tried to find acceleration using free body ...
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1answer
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Why does a falling ladder $y$ component force greater than the $x$ component force?

I have a ladder at 30* against the smooth wall and it accelerates down and to the left when it falls to a rough ground. It also pivots at the bottom. I understand that the the force of gravity is ...
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1answer
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Torque and a Stretched Rubber Band Wrapped Around an Axle

I have to define torque as it relates to my rubber band powered car that I made for my physics class, but the way I chose to build my car does not have any obvious torque-ish qualities as it relates ...
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1answer
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Why torque increases with arm length when same force is applied?

Just want to know why the door turns less (less torque) at the point closer to the hinge (point A) than at the outer point at the handle (point B) when the same force is applied. If same force is not ...
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Why is the center of mass the pivot of rotation?

Suppose a ball moves horizontally to the right and hits a vertical stick at a position closer to its upper end. I understand intuitively, the stick will have linear and angular momentum, and that it ...
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Moment of force about a point definition

In defining the moment of a force about a point as "the tendency of one or more applied forces to rotate an object about an axis [going through a point, hence also about a point]", I see it logical to ...
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2answers
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Not understanding the minus sign in the torque equation for a simple pendulum

The pic above is from Introduction to mechanics by Kleppner. In the torque equation they justified the minus sign because the torque has a clockwise sense. This makes sense to me if I pick the y axis ...
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1answer
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Why is the acceleration of a rotating body less than if it wasn't rotating? [closed]

Suppose an ideal string is passed from a pulley of any mass, (placed on a smooth horizontal surface), with sufficient friction so that the rope doesn't slide on it! Now if the pulley is attached to a ...
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4answers
152 views

Torque and force [closed]

Does the force due to torque on the edge of a wheel depend on the mass of the the wheel or is it always $\tau / R$?
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1answer
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Why does a drill-bit rotate at a constant angular velocity

When we use an automatic screwdriver ie: screwdrilling machine, we set the controls of the machine in such a way so as to rotate the drill bit at a certain fixed speed. But the point around which I ...
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Torque induced by drilling machines

A screw drilling machine, while constantly in use, delivers a torque on a screw. But if the drilling machine applies a constant torque on the screw, why does it, after a certain time period, look as ...
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Which way does a symmetric top precess and why?

I'm calculating the (instantaneous) rate of precession of a symmetric top (i.e. $I_1=I_2\neq I_3$) that is tilted at angle $\theta$ to the vertical if a torque $\vec{G}$ is applied, as shown below: ...
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What is the physics behind the motion of this sticky Spiderman toys?

A kid in my neighborhood was playing with a sticky Spiderman kind of toy. It looks like this: While observing it I noticed something peculiar that this toy had a tendency to climb down the wall ...
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1answer
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How does tension affect torque in a pulley

Let's say there's a pulley with a massless cord wrapped around it and tied to a mass below on the right. I know that torque is equal to α*Fsinθ. However, if I draw an FBD of the mass, T - mg = -ma. ...
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5answers
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Why torque is defined to have a direction as the axis of rotation?

Torque is generally defined as the "twisting force". Let's imagine that I have a rod of length $L$ pivoted at it's center. Now, let's assume that the shorter angle between the tail of the force ...
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How would a fluid having a vortex act under free fall?

Let us say we have an enclosed cylinder containing an ideal fluid , and we "swirl the fluid" such that a vortex is formed in the cylinder and the sides of the vortex are almost on the verge of sliing ...
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1answer
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Stabilizing a lightweight (empty) ship

Is it possible to stabilize an empty ship on high ocean waves with weights on long structures free to open up like wings by rotation on two vertical axis attached to the body of the ship simmilar to a ...
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2answers
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What is meaning of torque about an axis other than the axis of rotation?

Torque, for a system of particles, is defined as: $$\boldsymbol {\tau}_{net} = \sum_{i=1}^n \mathbf r_i \times \mathbf F_{i,net}$$ Here $\mathbf r_i$ is the position vector of the point from the ...
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4answers
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Is there a rotational analog for Newton's laws of motion? [duplicate]

In context of rotational dynamics my textbooks interminably states that there always exists a rotational analog for every linear variable and they are related to one another through similar equation. (...
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3answers
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Would the rod translate in this case, or only purely rotate?

If you have a rigid rod in space and apply an instantaneous upward force perpendicular to the very right of the surface so that it is a pure torque of 10Nm, will it only rotate or will it also ...
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2answers
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A question about the vertical part of the beam

I am solving beam type of problems finding reactions, moments...my question is how do I represent the F2 force that is acting on the vertical part of the beam (on the stick). Usually there is only a ...
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4answers
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Torque on accelerating tire

So I have a problem understanding the torques on a tire as it accelerates from rest. Suppose I have a tire with mass $m = 10kg$, radius $r = 0.5m$ and I apply torque with magnitude $\tau = 30Nm$ to ...
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1answer
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Tire traction force, friction or reaction? [duplicate]

I'm confused with the nature of the force produced by tires that pushes the car forward. This is what I understand: Let us have a driving torque applied on the wheel axle clockwise. This will produce ...
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4answers
116 views

Does $F=ma$ still apply when a force creates torque?

Consider a wheel and axle. I apply a force on the edge. That creates a torque. However, why doesn't $F=ma$ still apply? Aren't I still applying a force to the entire wheel/axle assembly, why doesn't ...
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Dynamic Modeling of Differential drive 2D robot

Usually Lagrange equations are used for dynamic modeling. In this paper "https://pdfs.semanticscholar.org/4e98/09960be9ec7f1ad8fadf61dad8cb1c8818d0.pdf", the resulting dynamic equations of motion is ...
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Rotational motion centre of mass

When any body like a pen is given a gentle hit why does it rotate about its center of mass? I gave my pen a hit from left end and executed circular motion about its center of mass? Why is it so?
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Torque due to a small block inside a cylinder on an inclined plane [closed]

If I have a small block inside a cylinder on a inclined plane. What is the torque on the cylinder due to the friction between the small block and the cylinder? It is easy if the center of the cylinder ...
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1answer
71 views

Torque of a compound pendulum

Let us consider a compound pendulum with the mass $m$ which moves along the $xy$-plane and rotates about the $z$-axis. Its pivot is at $(0, 0, 0)$, and the vector from the pivot to the centre of mass ...
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1answer
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How should it be approached the combined moment of inertia of a system and torque to find the angular acceleration of a system of pulleys? [closed]

I'm not very sure if the combined system of pulleys sharing a common radius should it be approached if it would be a single one. In either case, what would be the way to assess that situation?. To ...

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