Solving the Spring-Weight Paradox: 0.039m

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SUMMARY

The discussion revolves around solving the Spring-Weight Paradox, specifically addressing the maximum stretch of a spring when a weight is applied. The participant initially calculated the maximum stretch as 0.01962 m using the formula Fs = -kx and w = mg, but the solution key indicates the correct maximum stretch is 0.039 m. The discrepancy arises from the need to apply the conservation of energy principle rather than just force equilibrium, particularly when considering sudden changes in weight, such as adding a brick to the basket.

PREREQUISITES
  • Understanding of Hooke's Law (Fs = -kx)
  • Knowledge of gravitational force (w = mg)
  • Familiarity with the concept of equilibrium in physics
  • Basic principles of conservation of energy
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  • Explore advanced applications of Hooke's Law in dynamic scenarios
  • Learn about the effects of sudden forces on equilibrium states
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Homework Statement


upload_2014-11-23_7-54-12.png


Homework Equations



Fs = -kx

w = mg

The Attempt at a Solution



I said that when the spring is stretched out at its max, the weight pulling down will equal the force of the spring pulling up.

Fs=w
-kx = mg
-(1500)(x) = (3)(-9.81)

x = 0.01962 m

The solution key tells me the max stretch is double this amount, 0.039 m. What is wrong with my approach?
 
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Mark the word suddenly. If the basket were at maximum distance and forces would be in equilibrium, the velocity wouldn't change anymore, so the thing would hang still.
Do you think that is what would happen if you suddenly put a brick in the basket ?
 
Last edited:
Ah. I see. So then I need to solve the problem using the conservation of energy.
 

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