This came up in a movie I watched recently: a golfer was tyring to make a simple putt (3 or so meters) on a perfectly flat, level green. Because reasons, the green was rotating clockwise at a certain number of RPMs (use whichever number of RPMs is easiest for you to use when you do your calculations, and assume that the hole is at the center of the green, and the radius from which the green rotates). If this happened in real life, what would happen to the ball, and how could the golfer compensate?
I believe that the ball is going to go off in one direction or the other, but I can’t grok which. The golfer, I think, would have to hit opposite to the direction the ball is going to go.
If the centre of rotation is the hole, and the golfer plays the ball towards that hole, and the green rotates clockwise, then the ball will be deflected to the left. This is an instance of Coriolis forces at work.
The ball in the video above is staying on the turntable because it can roll freely. In the scenario posed in the film we’ve got three potential options for what might happen:
The “turf” on the green is sufficient to hold the ball in place until struck, in which case Schnitte’s answer presumably applies.
The green is rotating too fast for the ball to stay in place but there’s still enough resistance from the turf to prevent it from rolling freely in all directions, in which case it would likely roll off the green (like the penny in the video).
The rotation of the green starts the ball in motion but once moving it is able to roll freely on the green like the ball on the turntable, in which case it stays on for a while but trying to putt it while also standing on the rotating green poses a whole new issue.
Based on a question I once heard:
If you are in a room and everything is like Earth but you are really on a rotating (for simulated gravity) space station, how would you know?
Answer: try to spin a coin. It will refuse to because of the conservation of angular momentum.
Specific to this thread, if the golf ball is rolling to the hole, how would conservation of AM affect it?
That’s not entirely correct. If the space station is spinning enough to provide 1-g of simulated gravity, you can spin the coin. It will drift and wobble due to the Coriolis effect, but it’ll spin. How much it drifts will depend on the size of the rotating arm. Small station = rapid rotation = noticeable Coriolis drift, very large station is slower rotation = less noticeable drift. At some given size, say a 200m station rotating at 2 rpm, the effect will essentially be negligible.
Notice that the reference frame we’re used to also rotates. Just very slowly, taking 24 hours to make a rotation. Yes, it’s true we’re not using that centripetal force due to rotation as pseudo gravity, but if you do something which is big enough and flies long enough for the rotation to become significant … then it’s significant.
OTOHm on a human scale throwing or hitting something, say of ~<150mph and ~<400 yards, Earth rotation can be ignored. It does have a real consequence, but it’s down in the noise of your measurement errors.
Found an old educational video I remember from college. At one point, they slide a dry-ice puck across a rotating table, and show the motion from cameras rotating with the table, and stationary to the earth. The whole video is interesting; super old fashioned, but does a good job showing how Physics is dependent on the frame of reference in which things are measured and perceived.
(I gather a dry-ice puck has a small bit of dry ice in it which produces a cushion of gas to reduce sliding friction. Rather like an air hockey table.)
The real answer I assume would be, “it depends on the radius of the spin…”
Fun Fact: Arthur C Clarke discussed rotating habitats in relation to making the movie 2001. The calculation was that to avoid disorientation (and possible nausea) from coriolis force and differential forces, the platform had to be 300 feet in diameter for a 1G centrifugal force. His solution for the spaceship Discovery, with the rotating “jogging track” - “…We just ignored that detail.”
Of course, we haven’t done any experiments with humans in rotating artificial-gravity environments. I wouldn’t be at all surprised if the Coriolis effects are something that you get used to relatively quickly, at which point it ceases to be disorienting.
The video I posted upthread shows Tom Scott doing just that. After a while he could throw something ‘straight’ across the rotating room. To show how used to it he was, when they stopped the room, they asked him to put his arms straight out in front of himself, but he put them off to the side, since that’s what ‘straight in front of himself’ felt like for the past 10 minutes.
There have been numerous experiments with people in centrifugal systems of simulated gravity (albeit not in freefall conditions) as seen upthread and performed by Human Adaptation and Countermeasures Officeof NASA Johnson Space Center, the European Space Agency, JAXA, and others. A relatively comprehensive survey of the field can be found in in Artificial Gravity edited by by [Gilles Clément and Angeli Bukley. In essence, it is more difficult than movies and television would have you believe, and while a person will adapt to certain aspects of working in a rotating field, the physiological problems with a dominant Coriolis component on the vestibular system are profound and require a large rotational radius to minimize to the point that it is tolerable.
