Help understanding dynamic equilibrium

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Homework Help Overview

The discussion revolves around the concept of dynamic equilibrium, particularly focusing on the equilibrium rule ƩF=0N and its implications for motion at constant speed. Participants explore how an object can be in motion while experiencing balanced forces, such as a box being pushed with a force equal to the friction opposing it.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the conditions under which an object can move at constant speed despite balanced forces. Questions arise about the necessity of an unbalanced force to initiate motion and the role of friction. Some participants consider scenarios where friction is absent and question the implications for net force and motion.

Discussion Status

The discussion is active, with participants raising questions and exploring different interpretations of motion and forces. There is an emphasis on understanding Newton's first law and the conditions for maintaining motion without an unbalanced force. Guidance is offered in the form of questions aimed at prompting the original poster to think critically about the concepts involved.

Contextual Notes

Participants are navigating the nuances of classical mechanics, particularly the distinction between motion and the forces required to change that motion. The absence of friction in some scenarios is a key point of discussion, leading to questions about the nature of forces and motion.

urbano
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Homework Statement



if the equilibrium rule states ƩF=0N, how can something move or be moving at a constant speed ? eg I push on a box with 50N and friction provides 50N back, resulting in ƩF=0N. So I am not providing more N than the box is resisting with. I thought something could only be moved if the moving force was greater than the resisting force ? otherwise wouldn't it be a stand still ?

Homework Equations


The Attempt at a Solution



****update*****

just had thought...I'd only need more force than the friction provided to get the box moving, but once moving and if at a constant speed then its motion is unchanged, thus the zero net force ?? And this then becomes the first law as now it is moving it will remain moving until an unbalanced force acts upon it ??
 
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Newton's first law. If the ƩF=0N, no change in motion occurs.
 
What if the box is sliding on the table by itself and there's no friction?
 
aftershock said:
What if the box is sliding on the table by itself and there's no friction?

If there's no friction, what's the net force acting?
 
gneill said:
If there's no friction, what's the net force acting?

That was directed at the OP, in hopes of him being able to figure out the answer to his question.
 
aftershock said:
That was directed at the OP, in hopes of him being able to figure out the answer to his question.

Ah. Sorry for pouncing then :blushing:
 
aftershock said:
What if the box is sliding on the table by itself and there's no friction?
hmmm I don't quite get what would make the box slide ? If ƩF=0 and there's no friction my guess would be there is no force...but then I don't get how the box would be sliding with no force on it
 
urbano said:
hmmm I don't quite get what would make the box slide ? If ƩF=0 and there's no friction my guess would be there is no force...but then I don't get how the box would be sliding with no force on it

What if it were already sliding?

Motion does not require a force. Only a change in motion requires a force.

This is an essential difference between Aristotelian physics and Newtonian physics :wink:
 

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