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Clara Chung
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The weight act on me and the normal force act on me should be canceled out, so where does the sense of weight come from?
Delta² said:The sense of weight comes from the sense of normal force. The way our body sensors are made, we cannot feel directly the gravitational pull, however we can feel the normal force (which normal force usually is equal and opposite to the (gravitational pull=weight)) via the sensors we have in our feet.
Also the reason we cannot feel directly the gravitational pull might have to do with general relativity theory, might have to wait for someone good in relativity to explain this to you.
I don't think we literally feel a downward force, we feel an upward force. BUT our brain does internally or should i say subconsciously, a thought "I feel an upward force from the floor so there must be something else pushing me downwards, cause our brain considers the floor to be a "passive" object which means it cannot exert a force unless ofcourse first it is acted by an opposite and equal force."Clara Chung said:As normal force points upward, why do we feel a force downward?
Why don't the sense of force(simply equal to weight) include the centripetal force which have a sense of pulling outward?Delta² said:I don't think we literally feel a downward force, we feel an upward force. BUT our brain does internally or should i say subconsciously, a thought "I feel an upward force from the floor so there must be something else pushing me downwards, cause our brain considers the floor to be a "passive" object which means it cannot exert a force unless ofcourse first it is acted by an opposite and equal force."
Clara Chung said:The weight act on me and the normal force act on me should be canceled out, so where does the sense of weight come from?
Delta² said:Also the reason we cannot feel directly the gravitational pull might have to do with general relativity theory, might have to wait for someone good in relativity to explain this to you.
Clara Chung said:When a person is accelerating upward in a lift. The sense of downward push is due to the fictitious force or the increased normal force?
Clara Chung said:For the case with the Earth, I think the reason we can't feel the pull is that the centripetal force is much smaller than the gravitational force, therefore there is a net normal force acting upward.
Clara Chung said:If the centripetal force is gravity, then why the normal force canceled out the weight?
The centripetal force is indeed much smaller than the gravitational force, but the net force is downwards (the normal force is just abit smaller than the gravitational pull). BUT it then again depends what you have in mind, seems you say centripetal force but you actually mean the centrifugal force.Clara Chung said:For the case with the Earth, I think the reason we can't feel the pull is that the centripetal force is much smaller than the gravitational force, therefore there is a net normal force acting upward.
I have a major disagree here. My view is that we do NOT REALLY feel the fictitious force , but it is the subconscious interpretation that our brain does that make us feel the fictitious force. For example when we are in an accelerating car, what we really feel is the backseat pushing us forward but our brain works in a subconscious level and thinks something like "the seat cannot be pushing me forwards on its own, there must be something (the fictitious force) pushing me onto the seat".For the case of a carousel, we don't feel the inward pull at all but only the fictitious force. For the case of a person in an accelerating car we don't feel the forward force but the backward fictitious force again. Is it related to relativity?
And the last force that is explained there is called the Tidal force. It is the same force that you would feel in a small black hole.Drakkith said:It is cancelled, but weight is not evenly distributed throughout your body. You have 95% or more of your weight pressing down on your ankles and feet, but only 10% or so of it pressing down on your neck. The normal force is likewise divided. 100% of it is pressing up on the soles of your feet, but only about 10% is pressing upwards on your head.
You sense weight because your body has to work to keep your head upright, your limbs from falling straight down, to keep you from falling over, etc.
You don't need to look to GR to explain this. It's because gravitation is solely attractive, so every part of your body is being accelerated towards the Earth at approximately the same rate. If there were a large difference in acceleration between your feet and your head you would feel it.
Delta² said:I don't think we literally feel a downward force, we feel an upward force. BUT our brain does internally or should i say subconsciously, a thought "I feel an upward force from the floor so there must be something else pushing me downwards, cause our brain considers the floor to be a "passive" object which means it cannot exert a force unless ofcourse first it is acted by an opposite and equal force."
If a fictitious force doesn't exist do you mean centrifugal force doesn't exist?Drakkith said:I'm in agreement with Delta. I can't see how you can feel a fictitious force since it doesn't actually exist. But that doesn't stop your body from thinking it does!
Clara Chung said:If a fictitious force doesn't exist do you mean centrifugal force doesn't exist?
Sorry I don't understand. If it doesn't exist why are there tools like centrifuge that utilize this force? It makes more sense if centripetal force doesn't exist respect to an inertia frame view.Drakkith said:Indeed. But that doesn't stop the concept of a centrifugal force from being useful in physics.
Clara Chung said:Sorry I don't understand. If it doesn't exist why are there tools like centrifuge that utilize this force? It makes more sense if centripetal force doesn't exist respect to an inertia frame view.
UsableThought said:What might be some comparable fictions? E.g. how about the useful convention in analyzing electrical circuits of assigning a direction to current rather than just sign?
Drakkith said:The first one that comes to mind is from geometric optics where reflection is treated as refraction but with the index of refraction as negative for the medium the light is entering. The refractive index of the medium certainly isn't negative, but it's useful to consider it negative since it allows you to use the same equations without having to remember more than one sign change.
Clara Chung said:As normal force points upward, why do we feel a force downward?
Clara Chung said:For the case with the Earth, I think the reason we can't feel the pull is that the centripetal force is much smaller than the gravitational force, therefore there is a net normal force acting upward.
The sense of weight is the result of the force of gravity acting on an object. Gravity is a fundamental force of nature that causes all objects with mass to be attracted to each other. The strength of gravity depends on the mass of the objects and the distance between them.
Our bodies perceive weight through a combination of sensory information from various systems. These include the vestibular system, which is responsible for balance and spatial orientation, and the proprioceptive system, which provides information about body position and movement. Additionally, our muscles and joints also play a role in sensing weight.
Yes, the sense of weight can be influenced by factors such as altitude, temperature, and even emotions. For example, at higher altitudes, the force of gravity is slightly weaker, so objects may feel lighter. Changes in temperature can also affect the density of objects, making them feel heavier or lighter. Emotions and perceptions can also play a role in how we perceive weight, as our mental state can influence our physical sensations.
The sense of weight and mass are often used interchangeably, but they are actually two distinct concepts. Mass is a measure of the amount of matter in an object, while weight is a measure of the force exerted on an object by gravity. Therefore, an object may have the same mass, but its weight can vary depending on the strength of gravity.
Yes, there is a relationship between the sense of weight and the sense of balance. Our sense of balance is closely connected to our perception of weight and is essential for maintaining an upright posture and stable movement. When our sense of weight is altered, such as when carrying a heavy load, it can affect our balance and coordination. Similarly, when our balance is compromised, it can impact our perception of weight.