Infinite acceleration on a string?

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Discussion Overview

The discussion revolves around the concept of infinite acceleration in the context of a string under tension, particularly examining the implications of the string's mass being negligible and the conditions under which infinite acceleration might be suggested. The scope includes theoretical reasoning and conceptual clarification related to forces and acceleration in physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the assertion that a net tension force would necessarily lead to infinite acceleration, suggesting that this conclusion might depend on the string being inextensible.
  • Another participant points out that if the mass of the string is negligible, applying Newton's second law (F=ma) implies that a finite force could result in an extremely large acceleration, approaching infinity in the limit.
  • A subsequent post seeks clarification on the relationship between force, mass, and acceleration, specifically whether a finite force on an object with negligible mass leads to infinite acceleration.
  • Further contributions reiterate that if tension varies along the string, it results in forces acting on sections of the string, which can lead to very large accelerations, and that the concept of infinite acceleration is noted as a theoretical construct rather than a physical reality.
  • One participant concludes that the author's reference to infinite acceleration is ambiguous, indicating a recognition of the complexity in the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the implications of infinite acceleration, with some agreeing on the theoretical aspects while others question the clarity and applicability of the concept in practical terms. The discussion remains unresolved regarding the interpretation of infinite acceleration in this context.

Contextual Notes

The discussion highlights limitations in assumptions about mass and tension, as well as the implications of applying Newton's laws in scenarios involving negligible mass. The varying interpretations of "infinite" acceleration also suggest a need for clearer definitions.

PhysicsKid0123
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I'm trying to figure out what it says in my book. Here is the link of the picture. http://i941.photobucket.com/albums/...oads/7D0D3CE4-A11E-4F0F-A2A5-836D03945AE5.jpg Could someone explain the part where it says "Otherwise, there would be a net tension force acting on the sections, and they would consequently suffer an infinite acceleration." Why does it necessarily have to be infinite? The only reason why I see it should be infinite is if the string is inextensible (unbreakable and maximally stretched) and if it so happened to not be straight it must have some infinite force so to not make it straight. Is my logic correct?http://[URL=http://s941.photobucket.com/user/markangela/media/Mobile%20Uploads/7D0D3CE4-A11E-4F0F-A2A5-836D03945AE5.jpg.html][PLAIN]http://i941.photobucket.com/albums/ad259/markangela/Mobile%20Uploads/7D0D3CE4-A11E-4F0F-A2A5-836D03945AE5.jpg
 
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The mass of the string is assumed to be negligible. If you put that into F=ma, a finite force leads to an extremely large ("infinite" in the limit) acceleration.
 
mfb said:
The mass of the string is assumed to be negligible. If you put that into F=ma, a finite force leads to an extremely large ("infinite" in the limit) acceleration.

What do you mean exactly by "put that into F=ma." You are saying that if there were to be some sort of force or tension then a approaches "infinity" as m approaches "zero" in some sense?
 
If tension would be different in different parts of the string, then there would be a force acting on a section of string.

A force acting on an object with a very small mass will lead to a very large acceleration (as F=m*a).
A force acting on an object with a very very small mass will lead to a very very large acceleration.
A force acting on an object with zero mass will lead to an "infinite" acceleration. (note the " ", because this does not exist in reality).
 
mfb said:
If tension would be different in different parts of the string, then there would be a force acting on a section of string.

A force acting on an object with a very small mass will lead to a very large acceleration (as F=m*a).
A force acting on an object with a very very small mass will lead to a very very large acceleration.
A force acting on an object with zero mass will lead to an "infinite" acceleration. (note the " ", because this does not exist in reality).
Okay I think I see now. So the author's use of infinite accel. is ambiguous.
 

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