Tough question about reaction force Newton's third law -- Please help

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Homework Help Overview

The discussion revolves around a problem related to Newton's third law and reaction forces, specifically focusing on calculating forces and accelerations in a system involving multiple masses.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore the relationship between force, mass, and acceleration, questioning how to derive a specific answer from their calculations. There is discussion about which mass to use in the calculations and how it affects the outcome.

Discussion Status

Participants are actively engaging with each other's reasoning, with some guidance offered on how to apply the calculated acceleration to the second block's mass. There is recognition of confusion regarding the variables used in the problem.

Contextual Notes

There is a noted ambiguity regarding the use of different masses in the calculations, and participants are encouraged to consider all relevant forces acting on the masses involved.

bomberkid
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Homework Statement


. question is as attached. answer is 2f/5..how do u get this?

Homework Equations


F=ma
F= (5m)a
a= F/(5m)

The Attempt at a Solution


gotten a=F/5m , but why the answer is 2f/5?
 

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What force is necessary to produce your calculated acceleration in the second block?
 
F?
 
No... you calculated the specific ##a##, now put that back into ##F=ma## along with the second block's mass

Unfortunately the confusion between the abstract "F" and the specific "F" in this problem is perhaps making understanding a little harder than it should be.
 
I see. Why not use the mass 3m?
 
bomberkid said:
I see. Why not use the mass 3m?
Either will do provided you bring all relevant forces acting on the mass into the equation.
 
but if i were to use f=3m, and a is F/5m, i wouldn't get 2f/5 as the answer
 
bomberkid said:
but if i were to use f=3m, and a is F/5m, i wouldn't get 2f/5 as the answer
You get the right answer if you bring in all forces acting on the mass and do the algebra correctly. Please post your working.
 

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