In sci-fi with “spinning” ships to make gravity, how does someone drop something and it lands at their feet?

Question

This fogs my brain every time I watch one of these shows and I feel like maybe I’m completely misunderstanding the physics.

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You’re in a “ring” ship. The ring spins. You’re standing on the inside of the ring so it takes you along with it, and the force created “pins” you to the floor, like a carnival ride. Ok, fine.

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But that’s not gravity, and it’s not “down”. Gravity is acceleration, so what keeps the acceleration going in the ring ship is that you are constantly changing your angular momentum because you’re going in a circle. Ok, so when you let go of something, like a cup or a book, wouldn’t it go flying towards the floor at an angle? If you jumped wouldn’t you look like you rotated a little before you hit the ground, because you’d, for that moment, be continuing the momentum of your angular velocity from when you left the floor and the room would continue on it’s new, ever turning, course?

Wouldn’t it kind of feel like walking “uphill” one direction and “downhill” the other, with things sliding about as the room “changed” direction constantly?

Am I just COMPLETELY missing this idea and creating a cause and effect that doesn’t exist?

In: Physics

Answer 1

If they ‘drop’ something then that object is no longer experiencing any forces.

As such it will continue in a straight line…which intersects with the floor eventually. As the object moves in a straight line, you are also swept sideways by the rotation (that you had with the object) so that when the object connects with the floor your feet are there as well.

Significant changes in height can cause odd trajectories. The object held aloft in a spinning ring is actually moving with the same angular speed, but a lower linear velocity. this means that as it moves ‘down’ it’s lower speed will cause it to be left behind by the faster moving ‘lower’ objects closer to the rim.

So instead of seeing it fall straight down, it’ll drift or curve ‘back’. Likewise any object thrown up will curve ‘forward’ as it starts with a higher velocity near the rim, compared to any objects closer to the axis.

In large rotating objects this won’t be to noticeable, as the change in radius from a persons head to feet is small compared to the overall radius of the spinning structure. But small enough structures, or large enough falls would create a noticeable effect.