JCooper
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 Apr 25 comment How important is it, really, to clean vacuum parts? Haven't we all done that? Hah! Jan 3 comment Can any physical rigid body be represented by an ellipsoid with the same angular dynamics? Perfect. Thank-you. Jan 24 comment The Double Integrator: Matching velocity and position as quickly as possible with only a limited amount of force available Perfect. Thanks. It seems unintuitive that a bang-bang strategy would be optimal, but what you've illustrated makes sense. It's also interesting how the critical damping co-efficient of $\zeta=1$ is built into the configuration space as a slope of $\pm 1$. Dec 24 comment Converting angular velocity to linear velocity through friction Conservation of energy seems right. This should work for what I need (although I'll need it in 3d; so $\omega r$ needs to be $\omega \times r$ which means that I've got to do a little bit of playing to solve for $v_1$). Thanks. Nov 23 comment How do you combine two rigid bodies into one? @Qmechanic I really did want to know where the velocities go if two independent bodies become a single rigid body. However, as an after-thought I wanted to know if you can talk about the instantaneous velocities of a single system composed of multiple independent rigid bodies. E.g., if a ballistic rigid body were to fracture into multiple pieces, the linear and angular momentum of the system should be conserved; so I wonder if you could add up the pieces and get a measurement of the instantaneous linear and angular velocities of the system. Nov 23 comment How do you combine two rigid bodies into one? Okay. Works for me if no one's going to disagree. Would this still hold to describe the instantaneous state of the combined system if the two bodies weren't actually rigidly combined? Nov 22 comment Why does the Moon face Earth with the same side? Probability of any satellite being symmetrical seems to be rather small. But the planets don't seem to experience tidal-lock with respect to the sun. How many of the other planet's moons experience this in the solar system?