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You are at the center of a sphere, and there is no net gravitational force on you. Which of the following do you most agree with?
**Assume you are a point particle**
**Assume you are a point particle**
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DaleSpam said:Not only are there no net forces, there are also no tidal forces. That means that there are no internal stresses as you would get from being pulled equally in all directions.
Nugatory said:Nicksauce, are you making a point about the difference between the idealized problems we see in physics classes and real-world problems?
nicksauce said:My real reason for posting this is that I got in an argument about it with someone today and we spent a while on it. So I am now curious what other people think.
nicksauce said:Yes of course there is no force. The real question is give that there is no force, what, semantically is a better description of that fact.
If this is a point particle, it is meaningless to talk about anything but a net force. A point particle does not have internal stress. Being pushed and pulled in different directions is something that can only be experienced by macroscopic bodies.Vorde said:I think the most useful thing to say is that you are being pulled equally in all directions. Then you don't have to change anything about the way you are thinking if you want to talk about the gravitational potential somewhere else.
(Of course experimentally the two viewpoints are the same)
Why would I have to change my way of thinking to talk about the gravitational potential somewhere else? Everywhere is the same rule, you are pulled in the direction of the gradient of the potential. So if the potential is constant you are not being pulled, if it is not then you are.Vorde said:I think the most useful thing to say is that you are being pulled equally in all directions. Then you don't have to change anything about the way you are thinking if you want to talk about the gravitational potential somewhere else.
(Of course experimentally the two viewpoints are the same)
If the student said that the forces on a body were equal and opposite, he/she should be asked to do a free-body diagram and try to explain why there are no tensions within the body to balance these opposing forces.Vorde said:I guess you're right, and when I tried to extend my line of reasoning to other scenarios I found that it failed. However I still think (after admitting defeat, as it were) that were I explaining gravitational potential to a student, if the student said that all forces were equal and opposite at the center and therefore cancel I would nod and move on, whereas if the student said that there is no force at the center I would pause to make sure he understood correctly.
A quick poll on a semantic matter is a survey or questionnaire that is conducted to gather opinions or preferences on a specific semantic issue or topic. Semantic matters refer to the meaning or interpretation of words, phrases, or symbols.
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