How Can I Solve This Newton's Forces Problem for My Homework?

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Homework Help Overview

The discussion revolves around a Newton's forces problem involving friction, tension, and acceleration in a system of blocks. Participants are attempting to analyze the forces acting on the blocks and the role of static and kinetic friction.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are exploring the relationship between static and kinetic friction and questioning the conditions under which each applies. Some are attempting to apply equations of motion and free body diagrams to analyze the forces, while others express confusion about the use of mass in calculations and the nature of the forces involved.

Discussion Status

There is an ongoing exploration of the problem with various interpretations being discussed. Some participants have provided insights into the force balance and the implications of using different masses in calculations, but there is no explicit consensus on the correct approach yet.

Contextual Notes

Participants are grappling with the definitions and conditions of static versus kinetic friction, as well as the implications of their teacher's approach to the problem. There is uncertainty regarding the correct application of forces and the setup of the problem.

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Homework Statement


ScreenShot2014-05-04at33239PM_zps8bf4c472.png


Homework Equations





The Attempt at a Solution


A)
I am not sure how to go about solving this. I would say no you can't find Us. Can you just say that you do not know when the object will move?
B) First I found acceleration x= 1/2 at^2, 18= .5a(9), a= 4.
Then I used the free body diagram of m1. Fk pointing to the left, Tension 2 pointing to the right.
T2- Fk= ma
10g - 5g Uk = (5)(4), but my teacher uses the mass of both the blocks, 5+ 10. I am not sure why...
 
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I don't understand how there can be static AND kinetic friction between M1 and the surface..
 
mrnike992 said:
I don't understand how there can be static AND kinetic friction between M1 and the surface..

Not at the same time, obviously...
 
Your mistake is that T2 is not 10g. Just do a force balance on M2 and you will see what it really is, and you will also find out why your teacher used (10 + 5).

Chet
 
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