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- Thread starter ahmhum
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- #2

turin

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- #3

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umm a mass hanging on a spring that is vertical

- #4

turin

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Do you think that this refutes conservation of energy? If so, how? And realize that there are many forces and factors envolved, so try to incorporate all of them in your explanation.umm a mass hanging on a spring that is vertical

- #5

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Using the following data:

k (Spring Constant) = 40.875Nm

x - Extension of Spring (below equilibrium position) = 0.01m (1cm)

Maximum Height Above equilibrium position = 0.009m (0.9cm)

Mass on the end of the spring = 0.4kg (4*100g slotted masses)

Using Hooke's Law : 0.5*k*x

= 0.5 * 40.875Nm

0.002044Nm = 0.002044 J

Now the gain in Gravitational Potential Energy (GPE) of the mass :

GPE = Mass * Gravity Constant (9.81N kg

GPE = 0.4kg * 9.81Nkg

I would appreciate it if anyone could validate the mathematical model I have used and either confirm that the data is suggesting that the vertical mass spring oscillator is going against the conservation of energy principle or point out a flaw in my method and how I can fix this?

- #6

turin

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- #7

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Then the GPE is the maximum height that the mass gets to.

At the start... all the energy is Elastic Potential (which i have calculated above for you)

then at the end... all the energy should be GPE

but there is more GPE than Elastic Potential... meaning ive got more energy than i started with... which shouldnt happen so far as i understand

- #8

turin

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How did you come to these conclusions? So, you hang a mass from the ceiling by a spring. Then, you pull it down to to some elevation and hold it still. Then, you let it go. Is that the situation? I realize that this is just a thought experiment, but try to write a set of instructions for someone to follow so that they could repeat your experiment. This will do two things: 1) help you organize your thoughts and practice being a scientist, and 2) help me see where you are neglecting something.At the start... all the energy is Elastic Potential ... then at the end... all the energy should be GPE

BTW, do you think that this situation violates Newton's second law?

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- #10

Doc Al

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The spring potential energy should be measured from theUsing Hooke's Law : 0.5*k*x^{2}

= 0.5 * 40.875Nm^{-1}* (0.01m)^{2}

0.002044Nm = 0.002044 J

Now the gain in Gravitational Potential Energy (GPE) of the mass :

GPE = Mass * Gravity Constant (9.81N kg^{-1}) * Height Change

GPE = 0.4kg * 9.81Nkg^{-1}* 0.019m = 0.074556Nm = 0.074556 J

- #11

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Can I double check with you that in a perfect system (ie no resistance/loss in energy) a spring extended 1cm down would result in a 1cm gain above the equilibrium position?

- #12

Doc Al

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Yes. If you pull the mass a distance XCan I double check with you that in a perfect system (ie no resistance/loss in energy) a spring extended 1cm down would result in a 1cm gain above the equilibrium position?

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