Length of Spring

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  • #1
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[SOLVED] Length of Spring

Homework Statement



A load of weight 400 N is suspended from a spring and two cords that are attached to blocks of weights 3W and W as shown. Knowing that the constant of the spring is 800 N/m, determine (a) the value of W, (b) the unstretched length of the spring.

http://img406.imageshack.us/img406/472/13213uv7.jpg [Broken]

Homework Equations



[tex]F_{s} = -k x[/tex]

The Attempt at a Solution



I have already worked through part (a), getting 62.8 N for W and in the process I got 281.712 for the [tex]F_{s}[/tex] of the system above.

Now from the picture above, I can figure that the length AB is 1110 mm using Pythagoreans. Whether that is relevant or not to figuring (b) out, I am not sure. I'm thinking that I need to find what the [tex]F_{s}[/tex] would be if there were no forces acting on the spring.
 
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Answers and Replies

  • #2
OmCheeto
Gold Member
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2,563

Homework Statement



A load of weight 400 N is suspended from a spring and two cords that are attached to blocks of weights 3W and W as shown. Knowing that the constant of the spring is 800 N/m, determine (a) the value of W, (b) the unstretched length of the spring.

http://img406.imageshack.us/img406/472/13213uv7.jpg [Broken]

Homework Equations



[tex]F_{s} = -k x[/tex]

The Attempt at a Solution



I have already worked through part (a), getting 62.8 N for W and in the process I got 281.712 for the [tex]F_{s}[/tex] of the system above.

Now from the picture above, I can figure that the length AB is 1110 mm using Pythagoreans. Whether that is relevant or not to figuring (b) out, I am not sure. I'm thinking that I need to find what the [tex]F_{s}[/tex] would be if there were no forces acting on the spring.
I would look at the relevant equation and attempt to determine if it can be expanded to include initial and final values.
 
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  • #3
You can determine angles using SOH CAH TOA. From there you can use components to work out your answer more precisely.
 
  • #4
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double post...
 
Last edited:
  • #5
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I would look at the relevant equation and attempt to determine if it can be expanded to include initial and final values.
Thanks, I got it!
 

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