Solving Spring Truck Problem 2: Compute Work, Speed, if Force is Conservative

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Homework Help Overview

The discussion revolves around a problem involving a spring that does not conform to Hooke's law, described by a force law that includes both linear and quadratic terms. Participants are tasked with computing the work required to stretch the spring and determining the speed of a mass attached to the spring as it returns to a specific configuration. The nature of the force exerted by the spring is also under consideration.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of work by substituting values into the force equation and question whether a simple multiplication of force and distance is appropriate given the variable nature of the force. There is a suggestion to calculate energy at specific positions and to consider integration for work done.

Discussion Status

There is an ongoing exploration of how to approach the calculation of work, with some participants suggesting integration as a necessary method due to the changing force. Multiple interpretations of the problem are being explored, particularly regarding the application of work formulas.

Contextual Notes

Participants are navigating the complexities of a non-linear force law and its implications for work and energy calculations. The discussion reflects uncertainty about the appropriate methods to apply in this context.

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2. A spring from the truck is found not to conform to Hooke’s law. The force law for this spring is
found to be:
F = – k1x – k2 x^2
where k1 = 52.8 N.m-1; k2 = 38.4 N.m-2.
a) Compute the work required to stretch the spring from x = 0.500 m to x = 1.00 m.
b) With one end of the spring fixed, a particle of mass 2.17 kg is attached to the other end of the
spring when it is extended by an amount x = 1.00 m. If the particle is then released from rest,
compute its speed at the instant the spring has returned to the configuration in which the extension
is x = 0.500 m.
c) Is the force exerted by the spring conservative or nonconservative? Explain your answer.

Ok, for a)

sub in the numbers for x = 1m and you get -91.2 N
sub in the numbers for x= .5m and you get - 36 N

So force is 127.2 N when the spring is stretched from .5 to 1m?

As W = F*x, do i just plug in x=.5m and F = 127.2 N?

Cheers
 
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In a and b. Calculate the energy in x = 0,5 and x = 1,00. You can't do a with the simple W = Fs because F is changeable.
 
KingOfTwilight said:
In a and b. Calculate the energy in x = 0,5 and x = 1,00. You can't do a with the simple W = Fs because F is changeable.
So you have to integrate?
 
Yeah, I think so,

Work done = Integral F.dx : Limits of integration are from x = 0.5 to x = 1.00
 
Naeem said:
Yeah, I think so,

Work done = Integral F.dx : Limits of integration are from x = 0.5 to x = 1.00
Cheers :smile:
 

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