Questions tagged [rotational-dynamics]
A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.
4,494 questions
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I have a dispute with a car service center, I hope you can help me argue the case [closed]
The auto repair shop claims that installing the cotter pin on the hub nut doesn't affect it. Although there are instructions online, they claim that an incorrectly installed cotter pin wouldn't affect ...
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What does it mean when physicists say: "An object rotates around any point you choose"?
I say that the Earth rotates around its center of mass (CoM), but physicists tell me "Earth rotates around any point you choose".
I do not understand how an object’s rotation can be ...
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What is the direction of Radial acceleration in the case where COM is not at the geometric center? [closed]
Consider the following diagram,
Here, we are given that the cavity is made in the disc, such that the center of mass shifts a distance r by 2 to the left, as shown.
If I consider the point P as the ...
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What is the condition for rolling here? [closed]
Ans given is 5, but theres no solution given for it, solution just says use energy conservation.
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How can I model the angular motion of a physical/compound pendulum driven by impulse at $t=0$ and experiencing increasing period lengths over time?
I have a ~5-foot-tall counterbalanced rigid pendulum mounted onto a bearing with an oscillation period of about 10 seconds. The pendulum receives an impulse force at $t=0$ to begin motion. The initial ...
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A paradox of the precession of a stick
I can see that a heavy flywheel around an axis experiences precession. But when I look at the equation:
$$ \dot{\omega} = (I \omega) \times \omega + \tau ,$$
where $\omega$ is angular velocity in the ...
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What is the Sun's obliquity to the invariable plane?
I'm trying to figure out the obliquity (rotation axis of a body) of the Sun but relative to the invariable plane of our solar system (which is primarily dominated by Jupiter, not Earth).
Various ...
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Could 3I/ATLAS be a fragment from a collision involving a TNO and an interstellar object?
Observations of 3I/ATLAS (C/2025 N1) suggest a highly anomalous object, distinct from both typical comets and previous interstellar visitors. Rather than proposing an artificial origin, I would like ...
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Rotating-wave approximation (RWA) for two-tone spectroscopy
I am having a hard time figuring out what the correct rotating-wave approximation (RWA) should be in a two-tone spectroscopy simulation. Apologies in advance for this being an easy question, I work ...
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Two spools linked via a pulley: only one rotates. How to conserve energy?
I know how to get the correct answer for the following problem using dynamics, but when I approach it using the energy formulation I get the wrong answer.
Two massive, identical spools are attached to ...
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What force(s) is rotation made of? [duplicate]
Can the rotation of an object be viewed as the result of two perpendicular forces ('push' and 'pull') that have combined? When I spin a wheel there is a 'push force' at a right angle to the wheel's ...
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Angular momentum conservation for a rolling ball after an initial impulse
First a ball gets an impulse $J$. Why can we say that $$Jh = I_cm w,$$ when it is clear that the friction force is also acting around the CM of the ball. When balacing forces around the CM we see that ...
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How to obtain the third gravitational potential term from this series?
In this paper the gravitational potential between a point mass and an extended rigid body is
$$
U = -\mathbb{G}m_1\int_B \frac{\mathrm{d}^3 \mathbf{Q}'\rho(\mathbf{Q}')}{|\mathbf{r} + \mathrm{C}\...
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What are the Euler-Lagrange equations of an approximated rigid body and a point planet interacting via gravity?
The potential due to a rigid body will be approximated using a Lagrange polynomial expansion as
$$
U(x,y,z)=-\frac{\mathbb{G}Mm_p}{r} - \frac{\mathbb{G}m_p(I_1 + I_2 + I_3)}{2r^3} + \frac{3\mathbb{G}...
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Can a Massless Pulley with no friction be treated as a massless circular object with no friction?
A pulley usually involves a rotating axle to change the direction of tension. However I read in my Textbook that for an ideal pulley, this need not be the case, and you do not need to consider any ...
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