Mass needed for static equilibrium compound pulley system

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hus8765
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Homework Statement


For what m1 will the illustrated pulley system be in static equilibrium if m2 = 60 kg?

Homework Equations

The Attempt at a Solution


im supposed to use the change in lengths but don't know how to do it
 
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  • Diagram of a compound pulley system: a fixed upper pulley over which a rope runs to mass m1 on the left and to a movable lower pulley on the right; a second rope from the lower pulley holds mass m2 below it. Dashed reference lines mark x1 and x2, with a downward arrow labelled g.
    Screen Shot 2015-03-05 at 14.52.56.png
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If it is static (no motion) then the lengths will not be changing. Look to free body diagrams and tensions instead.
 
gneill said:
If it is static (no motion) then the lengths will not be changing. Look to free body diagrams and tensions instead.
thanks a lot
 
Hello hus, welcome to PF :smile:

The change in length thingy is a good hint, though. But perhaps a little differently: If one of the two moves a little, does the other move just as much, half as much, or twice as much ? From that you can deduce the proper tension force to keep balance. And balance means no change of lengths allright.