Maximum Static Force before Blocks Slip

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Homework Help Overview

The problem involves two blocks, one resting on top of the other, with a frictionless interface between the lower block and the table. The upper block experiences a horizontal force, leading to an acceleration until the blocks begin to slip. The participants are discussing the forces at play, particularly focusing on static and kinetic friction.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are questioning how to initiate the problem, particularly whether to calculate the normal force first. There is also a discussion about the nature of the force acting on the blocks and the conditions under which they begin to slip.

Discussion Status

The discussion is ongoing, with participants expressing uncertainty about the initial steps to take. Some guidance has been offered regarding the perspective of the blocks and the forces involved, but no consensus has been reached on a specific approach.

Contextual Notes

There is a lack of clarity regarding the specific force that needs to be calculated, as well as the definitions of the static and kinetic friction coefficients in relation to the problem.

patchums
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An 6.40kg block rests on a 12.5kg block. The interface between the lower mass and the table is frictionless, but there is friction (static friction μs and kinetic friction μk) between the two blocks. A horizontal force F acts on the upper block and causes both blocks to accelerate. The acceleration of both blocks when they begin to slip is 2.0 m/s2.

fk=μkFN
fs=μsFN

I guess I have no idea how to start with this question. Am I supposed to find the normal force first and work from there? Where do I even go from there? Any help would be appreciated, thanks much!
 
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patchums said:
An 6.40kg block rests on a 12.5kg block. The interface between the lower mass and the table is frictionless, but there is friction (static friction μs and kinetic friction μk) between the two blocks. A horizontal force F acts on the upper block and causes both blocks to accelerate. The acceleration of both blocks when they begin to slip is 2.0 m/s2.

fk=μkFN
fs=μsFN

I guess I have no idea how to start with this question. Am I supposed to find the normal force first and work from there? Where do I even go from there? Any help would be appreciated, thanks much!

You haven't stated what it is you're trying to find...
 
Aw geez, sorry. I have to find the force at the time when the blocks start to slip.
 
patchums said:
Aw geez, sorry. I have to find the force at the time when the blocks start to slip.

Okay, so immediately before the blocks begin to slip they are essentially one large block...
 
Try to imagine by sitting on the lower block. What you see? Where should the force act?
 

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