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0answers
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 ...
0
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0answers
34 views

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 ...
2
votes
3answers
115 views

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 ...
0
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0answers
40 views

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 ...
2
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5answers
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?
3
votes
1answer
190 views

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. $-\vec{\nabla} U$) ...
1
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1answer
46 views

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 ...
0
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4answers
185 views

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 “...
-1
votes
2answers
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. ...
0
votes
1answer
70 views

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 ...
0
votes
1answer
103 views

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 ...
0
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2answers
758 views

Moment of a force about a given axis (Torque) - Scalar or vectorial?

I am studying Statics and saw that: The moment of a force about a given axis (or Torque) is defined by the equation: $M_X = (\vec r \times \vec F) \cdot \vec x \ \ \ $ (or $\ \tau_x = (\vec r \times ...
18
votes
4answers
8k views

Why does torque point perpendicular to direction of the motion?

I have an intuition problem calculating torque using the cross product formula. As for example let the magnitude of the force be 50 lbs and length of the wrench be one foot and you are exerting ...
0
votes
1answer
109 views

Caluculating torque as a vector product [closed]

Can someone please explain to me why the vector used for Force in calculating torque is F=3.0j when the problem explicitly states that the magnitude is 3.9N?
2
votes
1answer
275 views

Translation of Vectors

I am a bit confused about translation of vectors. In the first class in physics itself we are told that we can translate vectors as we like to the desired position to do whatever that we are trying ...
0
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1answer
48 views

Why isn't the tail of the Moment vector at the tail of the position and force vector?

When I was first introduced to the concept of the vector product, e.g. V=PxQ, I always saw P and Q drawn on a plane with a common point of origin, and V drawn perpendicular to the plane formed by P ...
1
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2answers
86 views

Short question about moment force

I have a question about moment Forces. Let $\mathbf{e_1}$, $\mathbf{e_2}$ be the unit vectors defining a Cartesion coordinate system $Oxy$. Let $\mathbf{F}$ be the force applied at point $A$.We have: ...
2
votes
2answers
114 views

When the resultant doesn't act on the same object as the components

I can understand what the resultant means when it acts on the same object as the components. What I don't understand is situations like this: If two oppositely parallel forces (red arrows in diagram) ...
0
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1answer
2k views

Moment of a force about a given axis

I have learnt in class about finding the moment of a force F about a point A using the formula M = r × F where r is the vector directed from A to the point of origin of F A textbook problem ...
-2
votes
1answer
405 views

What is the relation between dot product and torque? [closed]

what is the relation between dot product and torque? what is the objective of dot product in torque? what do we benefit from getting it?
0
votes
3answers
171 views

Torque and Angular Momentum Relation?

Suppose we have a tyre hanging in mid air and has a metal rod in the middle of the tyre. If we apply a force at the end of the tyre then a Torque will be produced. I heard from someone that if we ...
2
votes
1answer
66 views

Does pedaling a bicycle produce a leftward torque?

If toque is defined by $$ \mathbf{\tau} = \mathbf{r} \times \mathbf{F} $$ and we apply a force to the pedal as shown below, wouldn't there be a leftward force via torque about the crankshaft? Is it ...
5
votes
2answers
12k views

Why is a clockwise moment negative by convention?

My physics book states that by convention a clockwise moment is said to be negative and an anti-clockwise moment is said to be positive. I'm curious about the origin of this convention. My thoughts: ...
1
vote
2answers
154 views

Why is torque equivalent to $xF_y-yF_x $?

In Feynman's lecture on rotations in space, http://www.feynmanlectures.caltech.edu/I_20.html, he introduced the cross product by building upon a definition of torque he had derived in a previous ...
2
votes
2answers
649 views

What is the importance of torque direction? [duplicate]

I understand the right-hand rule and direction of the force on an arm, but what exactly is this 'direction' that results from the cross product of the vectors $T = r \times F$? On paper, what is this ...
1
vote
1answer
359 views

How can I calculate the torque on a body resulting from a spinning propeller?

If a quadcopter has all of its propellers spinning on the same direction, the body of the quad will obviously start spinning in the another direction. I know how to calculate the torque acting on a ...
0
votes
0answers
837 views

Adding multiple torque vectors together to determine resultant torque

I am working in a 2D environment, where there are multiple angular forces (torque) applied at an object. The way I calculated 1 torque "application", was by: ...
3
votes
2answers
1k views

Is torque still a vector in 2 Dimensions?

In 3D, torque is defined as $\vec{r} \times \vec{F}$ which is a vector, therefore having both a direction perpendicular to the plane of $\vec{F}$ and $\vec{r}$ and a magnitude of $\text{F}\cdot\text{r}...
0
votes
1answer
331 views

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 $\mathbf F$ ...
0
votes
1answer
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 ...
1
vote
3answers
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 ...
5
votes
1answer
407 views

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 ...
1
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1answer
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. ...
4
votes
4answers
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?...
3
votes
3answers
819 views

Why does the moment of force (aka. torque) depend on the perpendicular distance?

Couyld anyone explain how the lecturer concluded that $$(\underline{r_2} - \underline{r_1}) \times \underline{H} = \underline{p} \times \underline{H}$$
2
votes
1answer
3k views

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 ...
0
votes
2answers
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 ...
10
votes
3answers
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 ...
0
votes
2answers
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 ...
5
votes
4answers
1k views

Meaning of the direction of the cross product

I was doing calculations with torque and then I came across something very confusing: I understand that the magnitude of the torque is given by product of the displacement(from the center of rotation)...
0
votes
1answer
405 views

What causes a gyroscope to eventually rotate/fall over?

Hey so I've just learned about angular velocity and momentum and how torque changes it. Looking at a wheel spinning around an axis, with one end being held up by a rope, what causes the wheel to ...