hooke law

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  • hookes law
    • when a helical spring is loaded,it streches
    • the natural lengh is the normal lengh of the spring without a load on it
      • the differnece between the extended and natural lengh is the extension
        • the extended lengh is the lengh of the spring when loaded
        • extension=extended lengh - natural lengh
    • the extended lengh is the lengh of the spring when loaded
    • definition of hookes law
      • extension is proportional to the load,provided the proportional limit is not exceeded
        • what does the last part of hooks law mean?
          • springs are not invincable
            • at some point,you will add too much force that  it will not be able to return to its orignial shape
              • we can this point the elastic limit
                • the elastic limit on the graph is easy to spot as it is he point that the line will begin to curve
                  • because the line is no longer straight,it means f and e are no longer directly proportional,so hooks law is no longer obeyed
    • hookes law states that the extension of the spring,e, is directly proporational to the load,f
      • eqaution
        • f=k  x e
          • f=force/load applied to the spring(N)        k=the spring constant (N/cm of N/m) e=extension (cm or m)
          • if k is large the spring is stuff,if k is small,the spring is easy to extend
          • the spring consant can be caulculated using th graph with k=f divided by e
    • when we plot a force extension graph(f-e) we see two features
      • 1.the line goes through the origin(0,0)
        • these feautures tell me that the force,extension and variables are DIRECTLY PROPORTIONAL
      • 2.the line is straight
        • these feautures tell me that the force,extension and variables are DIRECTLY PROPORTIONAL
    • when the spring reached its elastic limit it no longer obeys hookes law
      • in the regin where the line is straight on the graph,the spring shows elastic behavoiur
        • this means that when the load is removed the spring goes back to its orignial lengh
          • if a load more than 7 (see pg 27) is applied to the spring,it goes beyond its elastic limit and so changes its shape permenantily
            • when the load is removed,the spring does not return to its orignial shape
              • this is called plastic deformation

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