Find Max Velocity of Object From Spring Force Equation

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Discussion Overview

The discussion revolves around finding the maximum velocity of an object using a non-linear spring force equation, specifically F(x) = 3.133x - 4.333x^2 + 5.333x^3 - 2.667x^4 + 0.5333x^5, while ensuring that the force does not exceed 12 lbs. Participants explore the relationship between force, potential energy, and kinetic energy in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests finding the value of x from the force equation to determine the maximum velocity, indicating a value around 2.5 inches.
  • Another participant points out that the equation does not conform to Hooke's law and recommends deriving a potential energy function through integration to find the work done on the spring.
  • A different participant emphasizes the need to use the work-energy theorem to solve for velocity, reiterating that the spring does not follow Hooke's law.
  • Concerns are raised about the nature of the force, with one participant questioning the non-restoring behavior of the force as it increases with distance from x=0.
  • Another participant agrees with the concern about the force not being restorative and suggests that a minus sign may be missing from the equation.
  • A later reply clarifies that the equation is not for a traditional spring but for package cushioning, confirming the correctness of the original equation and expressing gratitude for the assistance received.

Areas of Agreement / Disagreement

Participants express disagreement regarding the nature of the force and its implications for the system's behavior. There is no consensus on the interpretation of the force equation or the appropriate method to derive the maximum velocity.

Contextual Notes

Participants note that the spring force does not obey Hooke's law, which complicates the application of standard spring potential energy equations. The discussion includes unresolved questions about the behavior of the force and its implications for the system.

deesal
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I'm given the force of a spring in the form F(x) = 3.133x - 4.333x^2 +5.333x^3 - 2.667x^4+.5333x^5 and asked to find the maximum velocity of an object so that the force does not exceed 12 lbs

My approach was to find x from the force equation which was about 2.5 inches and then set the kinetic energy of the object equal to the potential of the spring and solve for velocity but I am not sure how to change the force equation to fit in 1/2 kx^2
could someone tell me if this is the wrong approach or how to change the equation please
 
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deesal said:
but I am not sure how to change the force equation to fit in 1/2 kx^2
The 1/2kx^2 applies to a spring that obeys Hooke's law (F = -kx), which is not the case for this spring. Derive a potential energy function for this spring in a similar manner, using integration to find the work required to stretch the spring.
 
F(x) = 3.133x - 4.333x^2 +5.333x^3 - 2.667x^4+.5333x^5

It seems to me you may have to take an integral to find the work done in compressing the spring to where the force equals 12lbs.

Then solve for velocity using the work-energy theorem. (This spring does not obey Hooke's law, so (1/2)kx^2 is irrelevant.

(Sorry Doc, I was typing before I saw your post).
 
What I don't understand is that the force doesn't seem to be restoring. If the object is at say +1.0, then your function means the force will also be positive. I don't understand how any spring could increase its force directed away from x=0, the farther you are from x=0.
 
DocZaius said:
What I don't understand is that the force doesn't seem to be restoring.
I agree. Looks like there's a minus sign missing.
 
it isn't an actual spring the equation is for package cushioning in a box the equation was right thanks for the help I got it
 

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