Chapter 5: Q5E (page 259)
In Problems 1–7, convert the given initial value problem into an initial value problem for a system in normal form.
[hint]
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Chapter 5: Q5E (page 259)
In Problems 1–7, convert the given initial value problem into an initial value problem for a system in normal form.
[hint]
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Use the result of Problem 31 to prove that all solutions to the equation\({\bf{y'' + }}{{\bf{y}}^{\bf{3}}}{\bf{ = 0}}\)remain bounded. [Hint: Argue that \(\frac{{{{\bf{y}}^{\bf{4}}}}}{{\bf{4}}}\) is bounded above by the constant appearing in Problem 31.]
A Problem of Current Interest. The motion of an ironbar attracted by the magnetic field produced by a parallel current wire and restrained by springs (see Figure 5.17) is governed by the equation\(\frac{{{{\bf{d}}^{\bf{2}}}{\bf{x}}}}{{{\bf{d}}{{\bf{t}}^{\bf{2}}}}}{\bf{ = - x + }}\frac{{\bf{1}}}{{{\bf{\lambda - x}}}}\) for \({\bf{ - }}{{\bf{x}}_{\bf{o}}}{\bf{ < x < \lambda }}\)where the constants \({{\bf{x}}_{\bf{o}}}\) and \({\bf{\lambda }}\) are, respectively, the distances from the bar to the wall and to the wire when thebar is at equilibrium (rest) with the current off.
Feedback System with Pooling Delay. Many physical and biological systems involve time delays. A pure time delay has its output the same as its input but shifted in time. A more common type of delay is pooling delay. An example of such a feedback system is shown in Figure 5.3 on page 251. Here the level of fluid in tank B determines the rate at which fluid enters tank A. Suppose this rate is given by where and V are positive constants and is the volume of fluid in tank B at time t.

b. Find a general solution for the system in part (a) when and .
c. Using the general solution obtained in part (b), what can be said about the volume of fluid in each of the tanks as ?
In Problems 3 – 18, use the elimination method to find a general solution for the given linear system, where differentiation is with respect to t.
Generalized Blasius Equation. H. Blasius, in his study of the laminar flow of a fluid, encountered an equation of the form . Use the Runge–Kutta algorithm for systems with h = 0.1 to approximate the solution that satisfies the initial conditions . Sketch this solution on the interval [0, 2].
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