How does friction affect the middle box in a double tension problem?

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Friction plays a crucial role in determining the net force acting on the middle box in a double tension problem. To analyze the system, it's essential to establish the direction of friction, as it affects the overall motion and tension in the connected boxes. The equations of motion for the hanging boxes must be combined with the frictional forces acting on the middle box to solve for the net force. Understanding how the hanging boxes influence the middle box's dynamics is key to finding the correct fnet equation. Clarifying these relationships will help resolve the confusion surrounding the problem.
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Im getting stuck on the fnet equation for the middle box. I don't really know where to start I can get the two fnet=ma equations for the boxes hanging and how do the boxes hanging on each side effect the system as a whole.
Thanks I know this is most likely an easy question !
 

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The first thing is to figure out which way friction will act on the middle box.
Post whatever you have.
 
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