problem-solving-with-strings-and-springs

Problem solving with strings & springs

What if the particle is fixed between two different springs?

• There will be two different tensions and extensions

  • For extensions, you can use and 

    • or, in the case of equilibrium extensions, and 

• You will need an extra equation relating to , found by summing all the lengths

  • e.g. if the total distance is  then

• Springs can go into compression, but if you’re not told (or it’s not clear), draw both springs under tension

  • If it turns out that or  are negative later on, then you know they were actually under compression

• If a particle is attached to the midpoint of a spring, you can either

  • Treat the spring as a whole 

    • The two tensions either side have the form where  is the total extension

  • Or treat the particle as being fixed between two half-springs, halving their lengths (natural lengths and extensions), but keeping the same modulus of elasticity (the material they’re made from hasn’t changed)

    • The two tensions either side have the form <img alt=”T equals fraction numerator lambda over denominator open parentheses l over 2 close parentheses end fraction open parentheses x over 2 close parentheses” data-mathml='<math ><semantics><mrow><mi>T</mi><mo>=</mo><mfrac><mi>λ</mi><mfenced><mstyle displaystyle=”true”><mfrac><mi>l</mi><mn>2</mn></mfrac></mstyle></mfenced></mfrac><mfenced><mfrac><mi>x</mi><mn>2</mn></mfrac></mfenced></mrow><annotation encoding=”application/vnd.wiris.mtweb-params+json”>{“language”:”en”,”fontFamily”:”Times New Roman”,”fontSize”:”18″,”autoformat”:true}</annotation></semantics></math>’ height=”72″ role=”math” src=”data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20xmlns%3Awrs%3D%22http%3A%2F%2Fwww.wiris.com%2Fxml%2Fmathml-extension%22%20height%3D%2272%22%20width%3D%22101%22%20wrs%3Abaseline%3D%2230%22%3E%3C!–MathML%3A%20%3Cmath%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3ET%3C%2Fmi%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmfrac%3E%3Cmi%3E%26%23x3BB%3B%3C%2Fmi%3E%3Cmfenced%3E%3Cmstyle%20displaystyle%3D%22true%22%3E%3Cmfrac%3E%3Cmi%3El%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmfrac%3E%3C%2Fmstyle%3E%3C%2Fmfenced%3E%3C%2Fmfrac%3E%3Cmfenced%3E%3Cmfrac%3E%3Cmi%3Ex%3C%2Fmi%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmfrac%3E%3C%2Fmfenced%3E%3C%2Fmath%3E–%3E%3Cdefs%3E%3Cstyle%20type%3D%22text%2Fcss%22%3E%40font-face%7Bfont-family%3A’math17f39f8317fbdb1988ef4c628eb’%3Bsrc%3Aurl(data%3Afont%2Ftruetype%3Bcharset%3Dutf-8%3Bbase64%2CAAEAAAAMAIAAAwBAT1MvMi7iBBMAAADMAAAATmNtYXDEvmKUAAABHAAAADRjdnQgDVUNBwAAAVAAAAA6Z2x5ZoPi2VsAAAGMAAAAsmhlYWQQC2qxAAACQAAAADZoaGVhCGsXSAAAAngAAAAkaG10eE2rRkcAAAKcAAAACGxvY2EAHTwYAAACpAAAAAxtYXhwBT0FPgAAArAAAAAgbmFtZaBxlY4AAALQAAABn3Bvc3QB9wD6AAAEcAAAACBwcmVwa1uragAABJAAAAAUAAADSwGQAAUAAAQABAAAAAAABAAEAAAAAAAAAQEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAgICAAAAAg1UADev96AAAD6ACWAAAAAAACAAEAAQAAABQAAwABAAAAFAAEACAAAAAEAAQAAQAAAD3%2F%2FwAAAD3%2F%2F%2F%2FEAAEAAAAAAAABVAMsAIABAABWACoCWAIeAQ4BLAIsAFoBgAKAAKAA1ACAAAAAAAAAACsAVQCAAKsA1QEAASsABwAAAAIAVQAAAwADqwADAAcAADMRIRElIREhVQKr%2FasCAP4AA6v8VVUDAAACAIAA6wLVAhUAAwAHAGUYAbAIELAG1LAGELAF1LAIELAB1LABELAA1LAGELAHPLAFELAEPLABELACPLAAELADPACwCBCwBtSwBhCwB9SwBxCwAdSwARCwAtSwBhCwBTywBxCwBDywARCwADywAhCwAzwxMBMhNSEdASE1gAJV%2FasCVQHAVdVVVQAAAAEAAAABAADVeM5BXw889QADBAD%2F%2F%2F%2F%2F1joTc%2F%2F%2F%2F%2F%2FWOhNzAAD%2FIASAA6sAAAAKAAIAAQAAAAAAAQAAA%2Bj%2FagAAF3AAAP%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%2F)format(‘truetype’)%3Bfont-weight%3Anormal%3Bfont-style%3Anormal%3B%7D%40font-face%7Bfont-family%3A’brack_sm2882ad605b1e27be87c7468’%3Bsrc%3Aurl(data%3Afont%2Ftruetype%3Bcharset%3Dutf-8%3Bbase64%2CAAEAAAAMAIAAAwBAT1MvMi7PH4UAAADMAAAATmNtYXA3kjw6AAABHAAAADxjdnQgAQYDiAAAAVgAAAASZ2x5ZkyYQ7YAAAFsAAAAkWhlYWQLyR8fAAACAAAAADZoaGVhAq0XCAAAAjgAAAAkaG10eDEjA%2FUAAAJcAAAADGxvY2EAAEKZAAACaAAAABBtYXhwBJsEcQAAAngAAAAgbmFtZW7QvZAAAAKYAAAB5XBvc3QArQBVAAAEgAAAACBwcmVwu5WEAAAABKAAAAAHAAACDAGQAAUAAAQABAAAAAAABAAEAAAAAAAAAQEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACAgICAAAAAg9AMD%2FP%2F8AAABVAABAAAAAAACAAEAAQAAABQAAwABAAAAFAAEACgAAAAGAAQAAQACI5wjn%2F%2F%2FAAAjnCOf%2F%2F%2FcZdxjAAEAAAAAAAAAAAFUAFQBAAArAIwAgACoAAcAAAACAAAAAADVAQEAAwAHAAAxMxEjFyM1M9XVq4CAAQHWqwABAAAAAABVAVgAAwAfGAGwAy%2BwADyxAgL1sAE8ALEDAD%2BwAjx8sQAG9bAB