# All Questions

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41 questions
11 views

### Magnitude of moment in 3d space

What's the magnitude of moment about O, if the vectors F, r1 and r2 all lie in the z-y plane? I know the magnitude of the moment is the cross product of force and the perpendicular distance from the ...
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### Torque/Cross Product [duplicate]

Ok! My question is, what is the physical meaning of the vector produced by a cross product? For instance, in torque, what does the cross product’s resultant vector mean? What does it tell me about ...
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### The direction of torque is so confusing [duplicate]

When I was studying cross and dot products, I learned that the cross product of two vectors A and B is perpendicular to both A and B. But my mind is unable to understand that. Since both A and B are ...
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### Mass is ignored in vector product of r(vector) and f(vector), why?

In this solution in the book, the mass is ignored after vector product of position vector and force vector. In both part a and b of the question it is the same. I was wondering what might be the ...
132 views

### Why is torque defined as $r × F$ and not $F × r$?

Is it merely due to popular convention or does it supply any special clarification regarding other physical quantities?
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### Is torque always equal to the derivative of potential energy with respect to rotation angle?

For any three-dimensional rigid body, the applied torque on that body is defined as: $\vec{\tau} = \vec{r} \times \vec{F}$ where $\vec{F}$ is the applied force on the object (i.e. $-\vec{\nabla} U$) ...
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### Torque acting on car trailers

My question: "Which car trailer below will be moved in a straight forward line?" Relevant info: All forces (represented by the arrows) in the diagram are equal in magnitude. The car trailer diagrams ...
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### The nature of Torque as a vector

I can’t comprehend torque’s role properly: 1: What is torque’s nature? Is it some kind of energy? Because its unit is (n.m) and (n.m) is similar to (joules) and it’s energy unit. 2: As we all know “...
116 views

### How to apply right hand rule to determine the direction of Torque?

I have just started out rotational dynamics but after solving a few questions I found that most of the answers are coming to be wrong because I could not determine the direction of torque correctly. ...
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### Expressing the magnitude of torque using dot product

I wanted to know if it is somehow possible to express the magnitude of the torque vector about some axis using some dot product of other vectors in the system (the position of the object, the axis of ...
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### Why is torque defined as $\vec\tau = \vec r \times \vec F$ instead of $\vec\tau = \vec F \times \vec r$?

I am facing problems in concept of torque and its applications. \begin{align} \vec\tau & = \vec r \times \vec F \quad\checkmark\\ \vec\tau & = \vec F \times \vec r \quad ✗ \end{align} Why it ...
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### How the torque/moment-of-force can be mathematically defined?

Given the definition of torque/moment-of-force $\mathbf F$ applied in $P$ with respect to the pole $O$ $$\mathbf M_O=\vec{OP}\times\mathbf F$$ and given that the vectors $\vec{OP}$ and $\mathbf F$ ...
169 views

### Would equations for a spinning top be an (x,y,z) vector [duplicate]

I am following the equations on this page, and for torque it is $mgr\sin\theta$, but I am curious about $r$. I am working on a game and I want to correctly model the top, and am curious if $r$ should ...
2k views

### Free vs bound vectors and torque

When considering basic Newtonian mechanics, we can treat vector as free and move their point of application at will. This is consistent with the affine nature of Euclidean space. However, when ...
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### Considering the theory of special relativity: Is torque still a vector?

Considering the theory of special relativity: Is torque still a vector? In classical mechanics it is easy: You have 3 axes and thus 3 planes. Every plane has its own torque so torque has 3 ...
586 views

### Torque definition and right hand rule not arbitrary

I have read the following: http://www.feynmanlectures.caltech.edu/I_20.html#Ch20-S1 The formula for $\tau_{xy}$ is derived in this chapter: http://www.feynmanlectures.caltech.edu/I_18.html#Ch18-S2. ...
36k views

### What is the difference between dot and cross product?

What is the difference between dot product and cross product? Why do we use cross product to find torque, why can't we use dot product? Also we use dot product to find work done and not cross product?...
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### Why does the moment of force (aka. torque) depend on the perpendicular distance?

Couyld anyone explain how the lecturer concluded that $$(\underline{r_2} - \underline{r_1}) \times \underline{H} = \underline{p} \times \underline{H}$$
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### Line of action force

The task is to reduce the two forces into a single net force and then find the equation of its line of action. I chose to find the net force and momentum with respect to the origin. The magnitude of ...
568 views

### Mathematically determining the direction of torque?

I need to mathematically derive the direction of torque in a 2D plane(clockwise/anticlockwise), for a physics engine. I have torque calculated, but it is always positive, so rotation always is in the ...
5k views

### Torque direction meaning

I apologize if this question is dumb, but I've looked all over for a straightforward answer and either I can't find one or the terms are too complex for me to understand. I have only a rudimentary ...
12k views

### Confused on how to properly use right hand rule

I am having trouble using the right hand rule properly and often find myself putting my hand in awkward orientations. I know you point your hand in the direction of $r$ and then point your fingers in ...