J.C.MacSwell

One caution is that statement is somewhat ambiguous. It is sliding backwards relative to the non inertial frame of the merry go round, not relative to the ground, the ground being what is referenced in the "direction of spin" of the merry go round. You have of course made it clear with the remainder of the description...as long as you don't go back to using the non inertial frame and conclude that there must be a real force pushing the jar outward.

That's correct. When that force is strong enough to overcome the maximum static friction it moves in the direction of the combined vectors. A free body diagram helps to see what will occur.

It reverses as soon as the applied force up the slope becomes greater than the gravitational component down the slope, while still in static range, and the mass moves when the applied force becomes greater than the gravitational component and maximum static friction force combined.

If the liquid is frictionless, isn't the viscosity assumed to be negated?

"If your theory is found to be against the second law of thermodynamics, I give you no hope; there is nothing for it but to collapse in deepest humiliation." Sir Arthur Eddington, Nature of the Physical World (1927) "The pursuit of perpetual motion is equivalent to dreaming about an everlasting tin of beer." String Junky, The Original Science Forums (2015) The alcohol content may be different, but the message remains the same.

When accelerating the spin, it can rise opposite the acceleration. This direction can become inward with the first part of the rotation, before it becomes outward...and can slosh around before becoming primarily outward.

In the Atlantic Provinces, University of New Brunswick in Fredericton, Dalhousie in Halifax, and I think Memorial in St. John's Newfoundland all have good Engineering programmes, though I am not sure about robotics in particular.

I think the OP might be referring to the extra dimensions posited in Kaluza-Klein theory or String theory. Interesting question. I would expect if they were expanding or contracting (assuming they exist) the laws of physics would be changing over time, unless they were all somehow geared to orchestrate or compensate each other in some manner.

I started to laugh at that, but stopped as I was heading for the ceiling

That sucker's pretty big... Agree with acme, an almost negligible gain from no air resistance, and you still have the extra weight and bulk of the suit to overcome

From the original post...I skimmed through but did not see it covered and had not seen this thread prior to today (IIRC) Does an electron in free fall radiate? (My thought would be no) Does an electron forced to stay at rest in a gravitational field radiate? (It must...correct?? or am I off base?) So I'm thinking electrons do not radiate due to gravitational forces (alone)

Hi KC No one is trying to imply cat's are smarter. It is just that they have evolved to land on 4 feet very effectively and very efficiently. A simpler method of merely rotating the tail does not achieve the same result. Their instinctive method is actually very clever and a little complicated, even if they have no real understanding of what they are doing.

Here you go again...

I'll go with the cats, that control the precession about other axes while counter rotating about the main one, enabling them to land on all four feet in best orientation. You can't do that by simply spinning your tail.

Your humble opinion would be correct. While the photons emitted are themselves massless, they contribute to the mass (invariant mass) of the box/system

Right. They can't change their angular momentum without outside help (forces)

That's why you don't even need something to counter spin...it can simply translate away, on a trajectory offset from the axis ...and then you have cat's that can land on their feet from any position, with no change in angular momentum at any point in their fall

Is the ball simply released with the system in a static position? What force would be required to maintain the lower ball at rest prior to collision?

I see a lot of new members get negative reps where they are not used to the way we tend to debate. It might help them to conform, but at the same time they end up somewhat in the hole starting out. I think it would help if anyone with negative reputation received an automatic +1 once a week.

"Be a cubical photon" for the win!

At the risk of sounding inane, "nothing", as we think we know it, may not be nothing after all. (or in this case before all, and possibly again after all) Turtles may be the best guess so far: "A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise." The scientist gave a superior smile before replying, "What is the tortoise standing on?" "You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!"" —Hawking, 1988

With apologies to Wolfang Pauli, it is NOT EVEN... ..."not even wrong"

For the Earth/Moon gravity, the force is the same, but opposite, on the Earth as it is on the Moon. The Barycenter is not a massive point effecting the GPEs For the Earth/Moon the changes in GPE are pretty close to proportional to displacement (marginal change in force over the distances discussed) If you jump in the air, the COM between you and the Earth stays in place (or on it's path), but of course (almost) all the energy of displacement goes to you. It is not split equally even though the mass displacement is equivalent (opposite) ...all because the Earth is so much more massive

The increase in GPE wrt distance to the barycenter. It is less for the Earth than the Moon.

WRT the barycenter the gain for the moon is much greater than that for the Earth.