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Lowering a Piano with 2 ropes.

  • Thread starter talaroue
  • Start date
  • #1
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Homework Statement


The two ropes are used to lower a 244.37 kg piano 9.47 m from a second-story window to the ground. How much work is done by gravity force? (T1=1805 N, q1=64°, T2=1112 N, q2=44°.)
C11P111.jpg


How much work is done by T1 force?
How much work is done by T2 force?

Homework Equations


Wt1= mgdTcos(theata)


The Attempt at a Solution



Wt1= mdTcos(theata)=RIDICULOUSLY HUGE and wrong lol. What is wrong with the way I am approaching this problem?
 

Answers and Replies

  • #2
dx
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The force on the piano due to gravity is just the weight. So the work done by gravity is (force)(distance moved in direction of force) = weight times the distance lowered.
 
  • #3
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mmhmmm. I understand that part. But the main problem is the tension parts
 
  • #4
dx
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Oh sorry, I didn't see there were two more parts to the question.
 
  • #5
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I am sorry, I mean the work done by the first rope. I was thinking tension in my head. I thought the equation i came up with is right? What is wrong with it?
 
  • #6
dx
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The vertical component of T1 is T1sin(θ), not T1cos(θ). You will also need to add a minus sign because the direction of displacement is opposite to this vertical component. So the work done by T1 will be -dT1sin(θ) (force times displacement in direction of force).
 
  • #7
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so the equation i should be using is Wt1=-d*sin(theata)*T

isn't T the force?
 
  • #8
dx
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What is d? Isn't it the displacement?
 
  • #9
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Yep! I got it thanks for the help I got it right but more importantly undersand where the anwser came from.
 

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