# Tagged Questions

A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.

47 views

### Pendulum motion equation issue

The differential equation that gives the equation of motion of a pendulum where: $m$ is the mass $L$ is the distance between the pivot and the body's centre of mass $g$ is the acceleration due to ...
39 views

### Rotation of join of two different rods when one is rotated [closed]

Two cylinders A and B made of same material and having same length of radii $r$ and $2r$ are soldered coaxially. The free end of A is clamped and the free end of B is twisted by an angle theta. The ...
52 views

### Conditions to impose for accelerations in systems of rotating pulleys [closed]

I do not understand completely how do rotating pulleys with ropes (that do not slip) work. Besides the equations of motions, which are clear to me, some conditions on the accelerations are needed to ...
44 views

### Does the centrifugal force affect stationary objects as seen from the inertial reference frame?

If an object is moving at the same speed as a rotating/accelerating frame of reference it's in contact with but in the opposite direction (making its displacement zero), would such an object be ...
47 views

### What is the relationship between $W_1$ and $W_2$? [closed]

I have a model which schematic is in the linked picture. Blue $A$ and $B$ are rotational joints, black and red shapes are rigid elements. $I_1$ is moment of inertia of black and red elements combined ...
121 views

### Difference between potential centrifugal energy and rotational/kinetic energy

I'm having troubles to understand the difference between kinetic energy and potential centrifugal energy in some situations. I make an example where I am confused. A object moves on a rod attached ...
75 views

### Impulse and momentum on a system of three particles (equilateral triangle)

I found this exercise on a textbook which provided solely the description of what is happening and the answers with little explanation. The solution being provided, I am mostly interested in ...
55 views

### If a disc is rolling on a surface, how do you verify that no slip occurs? [closed]

If I have the values for the coefficient of static friction (0.1) and all the other variables, how do I verify that no slip occurs?
103 views

### In pure translation why the body does not exhibit rotation only and only about the CM? [closed]

Suppose I have a rod in pure translation as shown in the picture with some constant acceleration. The two forces $F_1$ and $F_2$ act as shown. So clearly due to the definition of pure translation ...
52 views

### Does the rotational form of Newton's second law always hold?

Does the equation, $$\vec \tau=I\vec \alpha$$ (rotational form of the second law) always hold? If not, in what conditions does it hold true?
29 views

### What kind of motion is caused by nonzero torques about two parallel axes?

Say on a rigid body there are non-zero torques about two parallel axes. About which axis does it acquire a angular acceleration? I'm looking for a mathematical explanation.
52 views

### Rotating rigid rod in empty space [duplicate]

To begin, we assume there is a rigid rod in empty space which has no rotation with respect to the fixed stars. The frame of the rod is now an inertial reference frame, say $F$. 1) The rod now has a ...
100 views

### Will future spaceships for very long distance rotate?

I have seen in the movie Interstellar and The Martian they use the model of spaceship which rotate around it's axis. This is the spaceship model from Interstellar. This is spaceship model from The ...
213 views

### Why does Torque exist?

Specifically, why does force increase with the moment arm? What about making a perpendicular force farther away from the axis of rotation increases it? How does the moment arm cause that?
85 views

### Cylinder on an accelerated rough plane [duplicate]

The following figure shows a cylinder resting on a rough horizontal rug that is pulled out from under it with acceleration $a$ perpendicular to the axis of the cylinder. What is the motion of the ...
51 views

### Rotating movable pulley [closed]

I'm trying to understand how a movable pulley of mass $m$ and radius $r$, that rotates and doesn't slip actually works. Consider the picture, if a force is applied at the free end of the rope, are ...
223 views

### Conservation of angular momentum in broken pendulum

I'm having troubles in understanding the correct way to use the conservation of angular momentum. Consider the pendulum in the picture with a neglegible mass rope and a slender rode of mass M and ...
67 views

### Net force for circular motion

So today my physics teacher was telling us that the net force when discussing circular motion was actually the centripetal force. He didn't go further and I would like to know if there's any proof to ...
111 views

### How to find speed of rotation of gears from kinetic energy of falling body?

A pulley is fitted to the first driven shaft of compund gear train. Last driven shaft of gear train(gear 8) is fitted to the 12V DC generator (6W).Now to the rope extension at the one end of the ...
63 views

### Wheel Sinkage Depth

I am trying to make a realistic car physics simulation for my game and the current thing that I am fighting to solve is rolling resistance. Although it's effect is minimal, this is important concept, ...
24 views

### rotating jars and centripetal force

why does water rise up the sides of a jars that are spun in a circle. How does the centripetal force act on the water making it move away from the center of the circle? Also how does speed affect the ...
66 views

### Parallel axis theorem proof?

First, I thought theorems do not have proofs. Anyway, for parallel axis theorem, I was given that the addition of translational kinetic energy and rotational kinetic energy proves the parallel axis ...
63 views

### Torque on a right angle triangle [closed]

I am attempting a question regarding the torque on a right angle triangle. The triangle is pivoted along the adjacent axis, there is no force acting on the opposite side, however there is a 12N force ...
16 views

### How to determine the right motor to rotate things? [closed]

Me and my teammates are trying to produce a motorized rotating bench. we want to rotate the bench to the other side if one of them get wet by the rain. we are currently doing the proposal for our ...
60 views

### Rotational motion: A cylinder, sphere and hoop rolling down a ramp [closed]

I have a question about comparing different objects in rotational motion. In this scenario: A cylinder (with moment of inertia = $\frac{1}{2}MR^2$), a sphere ($\frac{2}{5} MR^2$) and a hoop ($MR^2$) ...
18 views

### Relevant Archemidan Spiral Theorems: An Enquiry

Basically what I'm doing is investigating the solar wind's outflow. As part of this investigation is included a fairly crude application of a more complex outflow solution to that of basic archemidian ...
50 views

### Converting torque to angular velocity

Given the torque of a system, is it possible to convert this torque to the angular velocity of the object? I calculated the torque exerted by wind on a blade, however, now I need the RPM. To get the ...
41 views

### Clarification on what inertia and area moments?

This is something I have never understood despite applying the formulas in many classes. What I'm hoping to find here is some clarification. My understanding is that the first moment of inertia is ...
38 views

### Rolling cylinder on frictionless inclined plane

A cylinder is kept on frictionless inclined plane. Why it does not roll (it slides only), although torque with respect to contact point is working on it (due to component of weight parallel to incline)...
51 views

### Where does the formula for the moment of inertia come from?

I think I 'understand' the concept of moment of inertia, but I don't see why it is proportional to r^2 (for a given point). Is the equation just empirical?
150 views

### Why do trees sway?

Resonance can also occur in three dimensions (such as wind induced swaying) I tried to make a free body diagram (I know it is terribly wrong) to find the forces that causes the tree to undergo ...
26 views

71 views

### Work done by a friction in rolling

When force is applied on extended objects at some point, the work done by this force on this object $\vec{F} \cdot \vec{dr_{P}}$ where $P$ is the point of application of force. When the object is ...
97 views

### Euler's laws - derivation

It looks simple and maybe is easy, but I don't get it. How to obtain the second equality from the first one below? Source: http://emweb.unl.edu/NEGAHBAN/EM373/note19/note19.htm They took ...
35 views

### What is the momentum change in a Foucault pendulum?

From the wiki page: If the plane of swing was north-south at the outset, it is east-west one sidereal day later. This implies that there has been exchange of momentum; the Earth and the pendulum ...
2k views

### How do I experience Earth's movement?

We are told that Earth is spinning on its axis at 1037 mph— something that we don't usually feel because of the environment that moves with us as well. Is there any experiment with which we can know ...
210 views

### To prove uniqueness of the rotation tensor associated with rotation of a rigid body

Suppose there are $N$ particles embedded in a rigid body which undergoes some random rotation such that: $$\overline{\overline {R}}_{ij} \otimes \vec{a}_{ij} = \vec{b}_{ij}$$ where, $i$ and $j$...
I'm trying to simulate vehicle powertrain and having problems at calculating correct impulse at the wheel. Here's what I have. Gear Ratio There are two gear ratio in the system $N_g$: ...