Friction Forces Between Stacked Blocks: Determining Direction

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Homework Help Overview

The discussion revolves around understanding the direction of friction forces between stacked blocks when one block is pulled. Participants are exploring the dynamics of friction in relation to acceleration and the interaction between the blocks.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to determine the direction of the friction force acting on the blocks based on their acceleration. Questions are raised about how to analyze free body diagrams (FBD) and the implications of different choices for the direction of forces.

Discussion Status

There is an ongoing exploration of the problem, with some participants providing insights into the expected behavior of the blocks under acceleration. Guidance has been offered regarding the relationship between the direction of acceleration and the resulting friction forces, although multiple interpretations are still being discussed.

Contextual Notes

Participants are considering the effects of different setups, such as the arrangement of books, and how these may influence their understanding of friction and acceleration. The discussion reflects a mix of assumptions and interpretations that are yet to be fully resolved.

minimario
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Homework Statement



UWQB18J.png

Homework Equations



F = ma

The Attempt at a Solution



When drawing a FBD for block 1, I couldn't figure out if the friction force between the blocks was toward the left or toward the right. Similar situation on block 2. How would I determine this?
 
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Which direction do you expect for the acceleration of the top block?

Technically you can choose both directions for the force, but one choice will give a negative value for the force.
 
Accelerate left. So the friction force would be left?
 
Which way do the dishes accelerate in this video?
 
To the right, but when I put a book on top of a heavier book and pull the heavier book right, the book goes left and falls off?
 
minimario said:
To the right, but when I put a book on top of a heavier book and pull the heavier book right, the book goes left and falls off?
No, the top book goes right. It falls off the left end of the bottom book because the bottom book accelerates faster than the top book.
 
Oh. So the friction on the top book would be right, and that on the bottom book would be left.
 
minimario said:
Oh. So the friction on the top book would be right, and that on the bottom book would be left.
Yes, that's correct.
 

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