Timeline for answer to Understanding conservation of angular momentum in relation with rotating objects by Vincent Thacker
Current License: CC BY-SA 4.0
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| when toggle format | what | by | license | comment | |
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| Apr 14, 2024 at 11:34 | vote | accept | Stallmp | ||
| Apr 14, 2024 at 11:31 | comment | added | PM 2Ring | FWIW, the centripetal acceleration on a body at the equator is ~0.0339 m/s^2, so it reduces the effective gravity by around 1 part in 290. | |
| Apr 14, 2024 at 11:27 | comment | added | Vincent Thacker | @Stallmp That acceleration is the inward centripetal acceleration. But this centripetal acceleration does not in itself change the angular velocity as being a radial force, it applies no torque and does no work. | |
| Apr 14, 2024 at 11:24 | comment | added | Stallmp | That's exactly one of my confusions laid out in my post. Rotation means that points are constantly changing direction, which implies an acceleration that is constantly going on. So the fact that this happens without a force does not make sense to me. I understand that this is from conservation of angular momentum, but still, it does not make sense due to this reason. | |
| Apr 14, 2024 at 11:22 | comment | added | PM 2Ring | @Stallmp It seems that you believe that the ball or Earth rotates because some force is making it rotate. But that's not the case. It's rotating because it has angular momentum, and nothing is preventing it from rotating. | |
| Apr 14, 2024 at 11:22 | comment | added | Stallmp | So if my understanding is correct, the fact that the Earth is spinning causes a centrifugal force on our body, but this is dominated by gravity right? Which acts in the opposite direction. | |
| Apr 14, 2024 at 11:19 | comment | added | Vincent Thacker | @Stallmp The force you feel is the normal force applied by whatever surface is supporting your body. And this normal force is the difference between gravity and centripetal acceleration, which is less than half a percent of gravity, even at the equator. So you still feel more than 99.5% of gravity. | |
| Apr 14, 2024 at 11:11 | comment | added | Stallmp | The rotation rate of the Earth is high though, namely 460 m/s or 1000 mph. So wouldn't the internal forces that keep the material in circular motion have to be high? | |
| Apr 14, 2024 at 11:08 | comment | added | Vincent Thacker | @Stallmp The internal forces do not cause Earth to spin. They hold it together. As for the centripetal force due to Earth's rotation, it is very small due to the rotation rate. The "gravitational force" dominates. | |
| Apr 14, 2024 at 11:06 | history | edited | Vincent Thacker | CC BY-SA 4.0 |
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| Apr 14, 2024 at 10:57 | comment | added | Stallmp | I see, so there is still an internal force which causes Earth to spin. But then, this internal force should be considered external according to the frame of a human that is sitting on Earth right? Why do we then not feel this internal force, i.e. constant acceleration that keeps the Earth spinning? It is true that we are 'moving' along the Earth at an instantaneous moment in time, but then the Earth is changing its direction, so there should be a force acting on us to change our direction along with the Earth, which we should be able to feel. | |
| Apr 14, 2024 at 10:49 | history | edited | Vincent Thacker | CC BY-SA 4.0 |
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| Apr 14, 2024 at 10:42 | history | answered | Vincent Thacker | CC BY-SA 4.0 |