Why is there "weightlessness" on the top of a verticle circle?

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Discussion Overview

The discussion centers on the concept of "weightlessness" experienced at the top of a vertical circular motion, particularly in the context of a plane flying in vertical circles. Participants explore the forces acting on an object in this scenario, including gravitational and centripetal forces, and the implications for perceived weight.

Discussion Character

  • Conceptual clarification, Technical explanation, Debate/contested

Main Points Raised

  • One participant expresses confusion about the concept of weightlessness at the top of a vertical circular path, questioning how weight can be canceled by another force when both weight and centripetal force act downwards.
  • Another participant explains that to maintain circular motion, a centripetal force is required, which at the top of the circle is provided by gravitational force, leading to a net force calculation that can result in weightlessness.
  • A different perspective is introduced, suggesting that if the object moves faster than the minimum speed required for circular motion, the direction of perceived weight may change, pointing upwards at the highest point.
  • One participant suggests using a free body diagram to clarify the forces acting on an object on Earth compared to those in circular motion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the explanation of weightlessness; there are competing views regarding the forces involved and their implications for perceived weight at the top of the circular path.

Contextual Notes

Some assumptions about the conditions for circular motion and the definitions of forces involved are not fully explored, and the discussion does not resolve the mathematical relationships presented.

1832vin
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i'm ashamed, that i never understand this, eventhough I'm studying quantum mechanics...

so... why is there "weightlessness" on the top of a vertical circular motion?
ie, if a plane if flying in vertical circles, why is there weightlessness while on the top of a circular path?
i mean, if it's weightlessness, that means that the wieght of the object is canceled by a force equal and opposite, leaing to no net force, not change in interia, and therefore weightlessness...

however, that's not the case...? on the top of a circlar motion/path, the wieght points down to earth, whilst the centripetal force is also pointing downwards... wouldn't that make the person to feel even more force applied downwards?

the answers always "the weight = centriplital force" but i don't get how does that mean "weightlessness"

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In order to stay in the circle, you need a force directed towards the center of the circle and with magnitude C=m\cdot \frac{\omega^{2}}{R}. At the top of the circle, you still need that force and the only force you have available is F=m\cdot g which is pointed downwards. Therefore, the net "weight" at the top of the circle is F-C=m\cdot g-\frac{\omega^{2}}{R}. From this formula you can see that F-C=0 when m\cdot g-m\cdot \frac{\omega^{2}}{R}=0.
 
Last edited:
In fact, if you are moving faster than the minimum speed to maintain the circular orbit, then your weight is pointing upwards when you're at the highest point.
 
Why not draw a free body diagram for an object sitting on Earth and see how it differs from what you drew?
 

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