Questions tagged [torque]

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

114 questions
5k views

Do objects rotate around the torque vector or its center?

If a sphere has a torque vector coming out of it at point A, would the sphere rotate about its center or the axis of the torque vector?
12k views

1k views

Right-angle lever paradox in special relativity

I remember to have read somewhere an interesting special relativity "paradox" considering two perpendicular rods $A$ and $B$ of equal proper length $L$ fixed at point $O$. In the "rest" frame equal (...
1k views

Why doesn't a block rotate due to friction?

In a horizontal surface, a block (cube) is sliding due to a sudden push. When the block slides, there is frictional force which is acting on the block. Frictional force will have a torque around ...
102 views

How do I handle elastic contacts in a simulation with friction [closed]

I'm trying to simulate a wheel as it hits the ground. Problem 1 Suppose a disc is dropped from a height. It has initial velocity of $-x,-y$ caused by throwing and gravity. It has no initial angular ...
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)...
1k views

Vibration to Torque: Magic Motor

In the this video the person cuts 6 grooves on a wooden pencil and mounts a paper propeller using a pin on the soft eraser side. As he starts rubbing the groves vigorously, the paper propeller starts ...
2k views

Why is moment dependent on the distance from the point of rotation to the force?

The formula for moment is: $$M = Fd$$ Where F is the force applied on the object and d is the perpendicular distance from the point of rotation to the line of action of the force. Why? Intuitively, ...
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. ...
1k views

Torque off center of mass rigid body

In order to obtain the equations of the motion of a rigid body, I need the applied torque about the center of mass $T_\mathrm{c}$. However, I have a torque that is applied off center of mass at the ...
481 views

Torque on a rod? [closed]

I've learned that the torque on an object is just $\text{perpendicular force}\times\text{radius}$ and that has worked well for things like seesaws but it doesn't take into account the torque of the ...
1k views

How can I relate linear and angular motion using a single formula? [closed]

I want to relate linear and angular motion using a single formula. Assume I have a 10m rod, and I apply a force of 5N on it, 2.5m away from the axis of rotation for 1s. How can I determine the ...
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 ...
4k views

How do levers amplify forces?

This is really bothering me for a long time, because the math is easy to do, but it's still unintuitive for me. I understand the "law of the lever" and I can do the math and use the torques, or ...
918 views

Would this box on the floor rotate based on friction?

There is a floor that friction is proportional to its velocity (like $F=-kv$) and there is a box with its width as $l$ and its height as $h$. (you may assume that $l$ is longer than $h$). It is on the ...
4k views

Force acting on a simple rigid body in space

So this is the question that's been bothering me: Say you have a simple rigid body in space that is at rest or traveling with only translational motion at a constant speed. Say that the body is ...
242 views

Equilibrium of a tower of 2-d blocks

In the image below, All the blocks are frictionless & identical with side of unit length, height $h$, weight $w$ & center of gravity at their geometric centers. The 2 lowest blocks are on ...
3k views

What is the meaning of “moment”?

What is the meaning of moment? I'm little confused about the word as there are some terms like moment of momentum, moment of mass, moment of force, etc. I want to know what exactly is meant by the ...
5k views

Why is torque the cross product of the radius and force vectors?

I understand the torque vector to be the cross product of the radius (moment arm) and force vectors, but that means the torque would be perpendicular to the radius and force vectors, which makes no ...
1k views

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?...
3k views

Torque on a falling object

If you drop a rod with a small mass on one end and a large mass on the other (initially parallel to the ground) does it rotate as it falls? If you take the pivot point to be the center of mass, then ...
2k views

Boomerang physics and aerodynamics

I posted a question before on this website asking how to build a boomerang for a project which can fly at least 200 feet, so how would I increase the flight path. A user responded with: slow down the ...
2k views

Sphere rolling up a step [closed]

A sphere of radius R is rolling without slipping with a velocity v and collides inelastically with a step of height h < R. What is the minimum velocity for which the sphere will be over the step? ...