# Questions tagged [torque]

This tag is for questions regarding to torque, which is a measure of the increase in angular momentum over time.

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### Does A Pivot Exert A Force

On a frictionless horizontal table, a uniform stick is pivoted at its middle, and a ball collides elastically with one end, as shown in Fig. 8.10. During the collision, what are all the quantities ...
• 13
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### Confusions in conservation of angular momentum and torque

Say someone is on a spinning object with heavy weights in his hands. He then pulls those heavy weights to himself and then the total angular speed is faster. We can explain this with conservation of ...
1k views

### Why can we treat a ball as a point mass to calculate torque?

A sphere of radius $R$ is supported by a rope attached to a wall as shown in the below figure. The rope makes an angle $\theta$ with respect to the wall. The point where the rope is attached to the ...
34 views

### Buoyant force on a stick making an angle theta with the vessel

I was solving this question The answer of the question uses balancing of torques. It uses $L=0.5$m I have problem with the fact that they have used buoyant force $F = \rho V g$. Marking the net ...
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### Calculating the amount of torque applied to to stop a rod rotating at some angular velocity

Consider a Rod AB, having length $l$ with non uniform mass density $\lambda (x)$ a function of length from the end A, is rotating at an angular velocity $\omega$ with fixed end A and free end B. ...
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### Calculating vehicle and tire acceleration with tire slipping

I'm attempting to simulate the motion of a vehicle with $N$ tires and I'm running into some trouble deriving forces/acceleration when adding friction and tire slipping into the picture. Here's an ...
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### Forces accelerating a tire

I'm attempting to write a little vehicle simulator and I'm working on calculating vehicle linear acceleration and tire angular acceleration. I'm trying to add in tire slipping and I'm having trouble ...
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### Why do objects with greater length feel heavier - and how to calculate perceived weight?

Consider this situation: As part of some training, you are asked to pull an object that is 100 feet long, weighing approximately 218 pounds across a distance of 310 feet (fire hose across concrete if ...
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### Can a translational torque cause a change in rotational angular momentum? gyroscope example

Please confirm if my understanding is correct: The example of a gyroscope suspended from a pivot is a case in which translational torque causes a change in the direction of rotational angular momentum:...
1 vote
47 views

### Does the direction of the torque acting on a car tire change depending on which direction the tire is rotating?

As I understand, the reason why unbolted car tires will fly off perpendicular to the direction of a moving car is because of the torque generated by the axel. This is unintuitive to me because there ...
21 views

### How can we find the angle between areal vector and magnetic field?

For finding torque we need to find the angle between areal vector and magnetic field. But areal vector makes an angle 37° with the x axis and that means it makes 53° with magnetic field because that's ...
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### In a magnetic field, does the force act on the midpoint of the current carrying wire?

Here, it says that the force acts on the middle points of the wires, but why? What do they mean by when they are saying that the forces 1 and 3 are acting on the same line of action? How does that ...
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### Why isn't the moment always included in a free-body diagram?

Now I have seen many times both in my physics book and other books when drawing a free body diagram the moment is not included but the forces are. For example in 2d when a beam is fixed to a wall ...
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### How does the centripetal force on the butt of a golf club's shaft produce torque that rotates the club/clubhead forward?

In the top picture, which is how torque is typically explained, the center of rotation is different than in the bottom picture. I think I understand how this works in the top picture, but I don't see ...
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### Spinning plate on the barbell

Suppose I have a plate and a barbell like the ones we see in the gym. When I spin the plat in the clockwise direction, the barbell also starts spinning in the clockwise direction. When I put my hand ...
• 1
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### Can torques cause both transitional and rotatory motion?

Imagine a rod (a rigid body) 10 meters long that is freely floating in space without being attached at any point. Its mass is 12 kilograms and according to most sources I found, its moment of inertia ...
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### How torque and linear force interact with forces on poles

When there are 2 forces normal to each end of a uniform pole, if they had the same force, the rotation would be cancelled out and all force would be acting in one direction. But if one force was ...
154 views

### What happens if we prevent gyroscope to precess?

If we apply some torque to spinning wheel in a vacuumed space in body frame y axis, wheel try to precess due to gyroscopic effect but it will be prevented by obstacles as seen from picture, what will ...
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### What determines the mechanical advantage of a lever?

This question is more specific than it seems. I am doing a mechanics-related project in class and we are learning about the functions of levers. Basically, I am confused as to what determines the ...
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1 vote
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### What is angular momentum and torque due to the center of mass? Give me an example

when I was studying angular momentum and fixed axis rotation in kleppner book, I had a topic on motion involving translation and rotation. On that topic, they said that components of angular momentum ...
1 vote
161 views

### Torque applying on both rotating and non-rotating object

In rod reference frame: origin is center of the rod, pitching axis is coinciding with the rod external torque is applied in rolling axis If a torque is applied to non-rotating object(the rod and the ...
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### What is the physical meaning of the torque term involving the magnetic displacement force?

In Zangwill's Modern Electrodynamics the magnetic torque is derived in Eq. 12.63 to be \mathbf{N}(\mathbf{r}_0) = \mathbf{m} \times \mathbf{B}(\mathbf{r}_0) + \mathbf{r}_0 \times \...
1 vote
141 views

### Is there a maximum angular acceleration due to gravity for a given radius?

I'm having trouble understanding the relationship between angular acceleration and tangential acceleration, specifically, how can an angular acceleration created by the tangential acceleration of ...
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1 vote
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### How are gears and levers related?

@1:46 https://www.youtube.com/watch?v=85qX5GwkSTY "Now the short arm moves 1/4 the distance, but we get 4 times the force" I do not understand what is meant by this part. This video is ...
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1 vote
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### What are the conditions for the uniform circular motion of this small ball? [closed]

As shown in the figure, one end of the rigid rod is a small ball, and the other end of the rod is supported on a plane. The gravitational field of the Earth is vertically downward, thus forming a ...
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1 vote
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### What is the point of torque?

I am having a hard time understanding torque. What is the physical significance of torque? Why is it defined as $\mathbf{r} \times \mathbf{F}$? I know that torque helps us to calculate the angular ...
86 views

### Energy due to force acting on a rod

Let us consider a rod of length $L$. We apply a force $F$ on this rod in a direction perpendicular to its length. There are two possible cases, we apply the force on the center of mass of the rod, or ...
43 views

### Is this an example of precession, or is its motion more complicated?

Let's say there is a solid cylinder floating in space and rotating about its axis of symmetry at rate $\omega$. At time t = 0 a force constant in magnitude is applied to the bottom of the cylinder. ...
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### Rotational mechanics in collision of a mass and a rod

Suppose a small particle of mass $m$ moving at a velocity $v$ collides with a rod at the end in a perpendicular direction to the rod. I am sure that the rod translated in the direction same as the ...
1 vote
100 views

### Why is the internal torque zero?

In an object, the forces that two particles exert on each other are equal and opposite to each other and the resulting torque on the particles are equal and opposite to each other.but we know that ...
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### Reference frame used to calculate torque in $\boldsymbol{\tau} = \mathbf{r}\times\mathbf{F}$

I know that in $\tau = I \alpha$, we are present in frame of axis. When we write $\boldsymbol{\tau} = \mathbf{r}\times\mathbf{F}$, are we present in the frame of the point about which torque is to be ...
38 views

### How to interpret the additive term in torque formula?

Torque formula for a body subjected to a force is: $\vec{M}$ = $\frac{\mathbb d\vec{L}}{\mathbb dt}$ + $\vec{v}_o$ $\times$ $\vec{p}$; where $\vec{M}$ is the torque, $\vec{L}$ is the angular momentum, ...
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1 vote
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### In gyroscopic effect of a quadcopter, why does precession cause torque, not vice versa?

I don't know if the header corresponds to my actual quest but i will explain. In quadcopter dynamic equations of Newton-Euler formation that I have encountered in all academic publications, torque ...
34 views

### Alignment and anti-alignment of spins in magnetic field

Let's say that we spins in a very strong magnetic field. Then, the spins want to align in the same direction as the magnetic field due to torque being exerted on the spins. However, it may happen that ...
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1 vote
83 views

### Dropping a stick down with an angle

Let's say that we drop a stick down with an angle, meaning that the stick is not parallel to the ground. Assume there is only gravity. Is it correct that the orientation of the stick will not change ...
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### When a wheel begins to roll on a flat surface, is it due to fulcrum generated at the contact point by friction?

[Edit: What I'm trying to understand is how any wheel rolls on a surface, instead of just spinning in place. I know that friction provides the force to make the wheel roll, but I'm unsure about the ...
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1 vote
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### Torque on tendon driven inverted pendulum

I have this setup of an inverted pendulum and need help figuring out the force-torque relationship. Let's start with the left pendulum, where I inserted all values I am interested in. The red arrow is ...
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### Nordic curl - force at the ankle

So, there is an exercise called nordic curl. Looks something like this: https://www.youtube.com/watch?v=_e9vFU9-tkc It is sometimes performed with someone holding your ankles down. How does the ...
8k views

### Where does "excess" energy go when a vehicle uses a lower gear to move at a given speed?

So I understand that a lower gear as advantageous when accelerating a vehicle or when driving up hill (e.g because you are having to accelerate against gravity). I know this is because of the ...
33 views

### Understanding conservation of angular momentum in relation with rotating objects

Conservation of angular momentum says that the angular momentum of a closed system will not change if there is no external torque applied to the system. For example, let's take the example of a ...
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### Couple on free falling rod [duplicate]

When free falling rod is punched at top then it would start rotating as shown below : But only force here is punch force so how does a couple form here? Gravity is present but isn't it along the axis....
35 views

### Substituting a force with a reaction torque in a non-solid body

A beam is fixed to a wall to the left A to a free support at B and gets a load P at C. The exercise is to calculate the reaction force at B and the deflection at C with elementary cases. They do this ...
In the Feynman lectures he derives the (mechanical) energy of a dipole $$U = -\boldsymbol{\mu}\cdot \boldsymbol{B} + \mathrm{constant}$$ by considering only the torque on it in a uniform field. He ...