A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.
4
votes
2answers
92 views
Thrust center in space
I have this dilemma: Suppose you have a space ship somewhere in deep space, where there is no drag force or substantial gravity. If the ship has a single engine situated in such a way that the center ...
-3
votes
2answers
189 views
Which Axis of rotation?
Let us consider a body , A, of arbitrary geometrical shape of mass m1. Now let it be translating with a speed v. Let us consider a small point particle ,P, of mass m2. Suppose it strikes A with a ...
2
votes
1answer
82 views
Approximating Rolling/Sliding in 2D Shape
I'm trying to find more information on how a 2D shape (could be defined by a function, such as ellipse, or by a polygon) will roll across a surface. The shape could be nearly circular or quite ...
0
votes
1answer
35 views
Rotational Kinetic Energy of a rigid root - Full workings Provided?
Part v is where I'm stuck.
Here is the question with my workings
If I can find Torque I can find L and using the equation $L=Iw$ I can find the w value and hence using $w=2pi*f$ I can prove it ...
6
votes
0answers
112 views
What determines the angle of the cushion on a pool table?
If you look at the cushions (bumpers) on a pool table, you'll see that they're not vertical. They're tilted inwards. About 10 years ago, I came across a physics exam in which one of the problems ...
6
votes
0answers
99 views
Nuclear Magnetic Resonance (NMR) Conceptual Questions
Let $M$ be the magnetic moment of a system. Below are the Bloch equations, including the relaxation terms.
$$\frac{\partial M_x}{\partial t}=({\bf M} \times \gamma {\bf H_0})_x-\frac{M_x}{T_2} $$
...
3
votes
0answers
73 views
Videos of changing the orientation of an astronaut in space
Kane, Headrick and Yatteau describe in their paper "Experimental investigation of an astronaut maneuvering scheme" possible maneuvers to change the orientation in space without external torque. Is ...
2
votes
0answers
234 views
Why does a coin falls faster when it's flipping as well?
From my experiments with measuring how fast a coin falls, I have consistently measured a faster falling rate for a coin that flips as it falls.
As an example, a coin dropping on its edge from height ...
2
votes
0answers
542 views
Forces and torques about the CENTER OF MASS of a physical pendulum
I'm currently stumped by the following situation. Say we've got a rectangular physical pendulum (think ruler with a hole-punch at one end).
It's trivial to analyze the motion of the pendulum with the ...
2
votes
0answers
147 views
Why do control moment gyroscopes exhibit “torque amplification”?
There are a number of articles that describe the benefits of using control moment gyroscopes (CMGs) over reaction wheels in inertial navigation applications. One of the primary benefits of using a CMG ...
2
votes
0answers
194 views
Levitation rotation speed involving laser acceleration, pyrolytic graphite and a vacuum
The experment would involve a small NIB magnet levitating between or on the diamagnetic material pyrolytic graphite, unlike other forms of levitation this doesn't require power to run such as ...
1
vote
0answers
60 views
Limitations on the choice of axis of rotation regarding rolling wheels
Consider a situation where a wheel is rolling without friction on a level surface. Call the center of the wheel $C$, the point where the wheel contacts the ground $G$, and some arbitrary other point ...
1
vote
0answers
249 views
Neglecting friction on a pulley?
So, this is how the problem looks:
http://www.aplusphysics.com/courses/honors/dynamics/images/Atwood%20Problem.png
Plus, the pulley is suspended on a cord at its center and hanging from the ceiling.
...
1
vote
0answers
47 views
Fading transition and rotation of and object in 2D
I'm looking for sources about I guess dynamics subject.
The model I'd like to solve is reduced to a question of:
How does a force applied on a certain point of an object results in both fading ...
1
vote
0answers
241 views
Rotational Dynamics Problem-Rod slipping against block
A uniform rod of mass m and length l is pivoted at point O. The rod is initially in vertical position and touching a block of mass M which is at rest on a horizontal surface. The rod is given a slight ...
1
vote
0answers
238 views
How equivalent are heat energy and work energy in connection with a spinning flywheel?
Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper.
Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
1
vote
0answers
184 views
How to model an accelerometer measurements on a car wheel?
I am working on kinematically modelling an accelerometer on a car wheel.
When working on the initial conditions, I am confused whether or not I should use the gravitational acceleration since there ...
1
vote
0answers
299 views
Should angular momentum change or it should not.?
Let us consider a body with an arbitrary shape. Let its center of mass be assigned coordinates (o,o,z) with respect to an origin.Now let us consider two equal and opposite forces acting on the body ...
0
votes
0answers
83 views
Equivalence between a charged rotating cylinder and a solenoid
Suppose we have a cylindrical shell of radius $r$ with surface charge density $\sigma$. Then we start rotating the cylinder at an angular speed $\Omega$. You can show that in this case the surface ...
0
votes
0answers
301 views
How to find Rotational and Translational Equilibrium of Hanging Masses on a Bar?
I am making a hanging mobile which needs to be done mathematically by calculating torque. The problem is, I can't seem to figure out how to solve for the distance of the two masses from the pivot ...
0
votes
0answers
131 views
Torque required to spin a disk along its diameter
How would I calculate (or simulate) this? I am only interested in the aerodynamic drag caused by the surface moving, not any other forces.
As far as I know, the only variables needed are the drag ...
0
votes
0answers
99 views
Assume a spool rolls down a slope with its body (not its ends) in contact with the slope
I was doing a little mental exercise and imagined the above scenario. I can intuitively see that in the described case, the smaller the diameter of the spool body, the larger the proportion of the ...
