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Two different springs in parallel

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



In a parallel spring system, the springs are positioned so that the 56N stretches each spring equally. The spring constant for the left-hand spring, kl, is 1.7Nm and the spring constant for the right-hand spring, kr, is 7.7Nm.[/B]


Homework Equations


Momentum Principle
s=mg/2k
ks= mg/s
[/B]


The Attempt at a Solution



I'm confused with how they'll stretch the same length.. need help

(1.7N/m)(56N)= 95.2m
(7.7N/m)(56N)= 431.2m[/B]
 
Last edited:

Answers and Replies

  • #2
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4,268
Check the units on your two equations.

If each spring stretches x meters, what is the force for each of the springs (in terms of x)? If the sum of the two spring forces is 56 N, what is x equal to?

Chet
 
  • #3
gneill
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Is that the entirety of the problem statement or was there a specific question associated with the description? Is there any other context we need to be aware of? A diagram perhaps?
 
  • #4
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Check the units on your two equations.

If each spring stretches x meters, what is the force for each of the springs (in terms of x)? If the sum of the two spring forces is 56 N, what is x equal to?

Chet
Is that the entirety of the problem statement or was there a specific question associated with the description? Is there any other context we need to be aware of? A diagram perhaps?
Screen Shot 2015-02-13 at 5.57.38 PM.png
 
  • #5
gneill
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20,802
2,779
Ah. Much clearer! The two springs are constrained to stretch by the same amount, and both contribute to the total force that supports the weight. You have to figure out what amount of stretching will result in the desired total.
 
  • #6
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Ah. Much clearer! The two springs are constrained to stretch by the same amount, and both contribute to the total force that supports the weight. You have to figure out what amount of stretching will result in the desired total.
Would I use s = mk/2k ? I am confused on this question because I am not sure how to find an equal stretch with a constant force between the two springs.
 
  • #7
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4,268
Would I use s = mk/2k ? I am confused on this question because I am not sure how to find an equal stretch with a constant force between the two springs.
Why don't you try answering the questions I posed in post #4? These will lead you directly to the answer.

Chet
 

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