Determine the tension in each section of rope

AI Thread Summary
The discussion revolves around calculating the minimum force needed to lift a piano using a pulley system and determining the tension in various sections of rope (FT1, FT2, FT3, FT4). The initial calculations for FT1 and FT2 were both found to be 0.5Mg, while FT4 was determined to be 1Mg. The user specifically sought help with FT3, initially guessing values of 1Mg and 0.5Mg but was unsure of the correct answer. Guidance was provided to draw a free body diagram (FBD) and apply Newton's first law to find the equilibrium of forces, leading to a successful resolution of the tension in FT3.
helppleaseee
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picture of problem:
http://img.photobucket.com/albums/v223/lilaznbabe/4_56.gif

(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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helppleaseee said:
1.
picture of problem:
http://img.photobucket.com/albums/v223/lilaznbabe/4_56.gif

(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?
 
Last edited by a moderator:
i initially thought it was 1...but that is wrong, then i thought .5 but something tells me that's not right. :frown:
 
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
 
yay! thanks soooo much i got it!
 

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