Infinite Objects: Seeking the Physics Behind the Math

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Infinite objects are considered unphysical because they lead to undefined scenarios in physics, particularly regarding electric fields. When calculating the electric field of an infinite charged plate, the potential energy can become infinite, creating problems in understanding the system's behavior. If a particle is like charged, it experiences an unbounded increase in kinetic energy due to constant repulsion. Conversely, if the charges are opposite, the particle can gain unlimited kinetic energy as it approaches the plate. Thus, the inability to choose a reference point at infinity stems from these unbounded physical implications.
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Homework Statement
What is the physical meaning of not being able to choose the referance point at the infinity for calculating the E field of an infinite object(or shape)?
Relevant Equations
No equations are needed, only a clear and simple verbal explanation which explains the phenomenon is needed.
I know how the math does not allow us to chose the reference point at infinity for infinite objects but I need to understand the underlying physics reason, not math reason.
 
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cemtu said:
Homework Statement:: What is the physical meaning of not being able to choose the referance point at the infinity for calculating the E field of an infinite object(or shape)?
Homework Equations:: No equations are needed, only a clear and simple verbal explanation which explains the phenomenon is needed.

I know how the math does not allow us to chose the reference point at infinity for infinite objects but I need to understand the underlying physics reason, not math reason.

Infinite objects are fundamentally unphysical. You cannot have an infinite charged plate; only a relatively large one.

The potential energy of a particle in the field of a uniformly charged infinite plate may be infinite. If the plate and particle are like charged, then there is no limit to the kinetic energy gained by the particle as it is repelled with constant force indefinitely. And, if the particle and plate are oppositely charged, then there is no limit to the kinetic energy that the particle may have if it starts from far away. The potential energy "at infinity" would, therefore, be infinite. Which is to say undefined.
 
thank you but I did not understand your explanation.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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