A book weighing 5 N rests on top of a table?

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    Book Table Weighing
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Discussion Overview

The discussion revolves around the forces acting on a book weighing 5 N resting on a table, focusing on concepts of static equilibrium, gravitational force, and normal force. Participants explore the implications of these forces and their interactions.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that the downward force from gravity (5 N) is greater than the upward force from the table.
  • Another participant counters that if the downward force exceeded the upward force, the book would not be in static equilibrium and would fall through the table, emphasizing that the normal force balances the gravitational force.
  • A question is raised about the cause of the downward force and whether the table's upward force counteracts gravity.
  • A detailed explanation is provided about the forces acting on the book, stating that the normal force from the table balances the gravitational force, resulting in no net force and thus no movement.
  • One participant expresses understanding after the explanation.
  • A single post simply states "Gravity," possibly indicating a focus on the gravitational force itself.

Areas of Agreement / Disagreement

Participants express disagreement regarding the relationship between the gravitational force and the normal force, with some asserting that the forces must balance for static equilibrium, while others question the implications of these forces.

Contextual Notes

There are assumptions about the strength of the table and the conditions under which it would collapse, which are not fully explored. The discussion does not resolve the implications of varying weights on the table's structural integrity.

Vivee=)
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This just crossed my mind. The downward force of magnitude from gravity is longer than the upward force of magnitude from the table. Which explains why the downward force of magnitude, the 5 N, comes from gravity. Am I right?
 
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I don't think that is true, because that would imply that the book is not in static equilibrium and it would fall through the table. The upward is due to the normal force, which is a result of molecular interactions. Think about it, Newtons second law is F=ma the book is not accelerating, and has a velocity of zero, so there is no net forces acting on the object therefore all forces are equal.
 
So if there's a downward force of magnitude (5 N) exerting on the book, then what is the cause of it? Ok, if it is gravity, then the table would just collapse. Is the downward force from the table pushing back up on the gravitational force?
 
Vivee=) said:
So if there's a downward force of magnitude (5 N) exerting on the book, then what is the cause of it? Ok, if it is gravity, then the table would just collapse. Is the downward force from the table pushing back up on the gravitational force?

It works like this:

You have a book resting on a table. It's not falling through it or anything weird like that. It's just sitting there. According to Newton, there must be no net force acting on this book, otherwise it would be accelerating according to F=ma - in other words, it would be moving somewhere.

So since the book is stationary, we know there's no net force acting on the book. But that doesn't mean there aren't any forces acting on it at all. We know that gravity is acting on the book. For your book, it's applying a constant 5N of force in the downward direction. But since the book isn't moving, there must be some force balancing the force of gravity. This is known as the normal force, and it's applied by the table in the upward direction, counteracting exactly the force of gravity. Thus the net force on the book is zero and it doesn't move anywhere.

The table doesn't collapse because it's strong enough to withstand the force of gravity on the book. Put a heavy enough mass on it, though - say a car or a really fat person :-p - and the table will indeed collapse. And there's no 'downward' force from the table on the book, only the upward normal force.
 
LOL, ok, I understand. Thank you. :)
 
Gravity
 

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