Determine the tension in each section of rope

In summary, the conversation discusses the determination of the minimum force needed to lift a piano using a pulley apparatus and the tension in each section of rope. The correct values for the tensions in FT1, FT2, and FT4 are Mg, while the tension in FT3 is still being determined. The tension in FT3 can be approximated by assuming all tension forces on the upper pulley act vertically and using Newton's First Law to solve for the value.
  • #1
1.
picture of problem:
http://img.photobucket.com/albums/v223/lilaznbabe/4_56.gif [Broken]

(a) What minimum force F is needed to lift the piano (mass M) using the pulley apparatus shown in Fig. 4-56? (Enter your answers in terms of some multiple of Mg.)
____ Mg (I got .5)
(b) Determine the tension in each section of rope: FT1, FT2, FT3, and FT4.
Tension in FT1?
____ Mg (I got .5)
Tension in FT2?
____ Mg (I got .5)
Tension in FT3?
____ Mg
Tension in FT4?
____ Mg (I got 1)

ok so i only need help on FT3...
thanks!
 
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  • #2
helppleaseee said:
1.
picture of problem:
http://img.photobucket.com/albums/v223/lilaznbabe/4_56.gif [Broken]

(a) What minimum force F is needed to lift the piano (mass M) using the pulley apparatus shown in Fig. 4-56? (Enter your answers in terms of some multiple of Mg.)
____ Mg (I got .5)
(b) Determine the tension in each section of rope: FT1, FT2, FT3, and FT4.
Tension in FT1?
____ Mg (I got .5)
Tension in FT2?
____ Mg (I got .5)
Tension in FT3?
____ Mg
Tension in FT4?
____ Mg (I got 1)

ok so i only need help on FT3...
thanks!
the best you can do is approximate it by assuming all tension forces on the upper pulley act vertically. You've got the others correct, so why not continue in the same manner to solve for FT3 in the same manner using Newton 1?
 
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  • #3
i initially thought it was 1...but that is wrong, then i thought .5 but something tells me that's not right. :frown:
 
  • #4
what is causing the tension in #3?

draw a FBD of the pulley with all the forces on it

in order for this system to be in equilibrium the sum of the forces must be 0,

so the forces up must equal the forces down
 
  • #5
yay! thanks soooo much i got it!
 

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