In Problems 112 use the Laplace transform to solve the given system of differential equations.
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Table of Contents
Textbook Solutions for Differential Equations with Boundary-Value Problems
Question
(a) Use the Laplace transform and the information given in Example 3 to obtain the solution (8) of the system given in (7). (b) Use a graphing utility to graph u1(t) and u2(t) in the tu-plane. Which mass has extreme displacements of greater magnitude? Use the graphs to estimate the first time that each mass passes through its equilibrium position. Discuss whether the motion of the pendulums is periodic. (c) Graph u1(t) and u2(t) in the u1u2-plane as parametric equations. The curve defined by these parametric equations is called a Lissajous curve. (d) The positions of the masses at t 0 are given in Figure 7.6.5(a). Note that we have used 1 radian 57.3. Use a calculator or a table application in a CAS to construct a table of values of the angles u1 and u2 for t 1, 2, . . . , 10 s. Then plot the positions of the two masses at these times. (e) Use a CAS to find the first time that u1(t) u2(t) and compute the corresponding angular value. Plot the positions of the two masses at these times. (f) Utilize the CAS to draw appropriate lines to simulate the pendulum rods, as in Figure 7.6.5. Use the animation capability of your CAS to make a movie of the motion of the double pendulum from t 0 to t 10 using a time increment of 0.1. [Hint: Express the coordinates (x1(t), y1(t)) and (x2(t), y2(t)) of the masses m1 and m2, respectively, in terms of u1(t) and u2(t).]
Solution
The first step in solving 7.6 problem number 21 trying to solve the problem we have to refer to the textbook question: (a) Use the Laplace transform and the information given in Example 3 to obtain the solution (8) of the system given in (7). (b) Use a graphing utility to graph u1(t) and u2(t) in the tu-plane. Which mass has extreme displacements of greater magnitude? Use the graphs to estimate the first time that each mass passes through its equilibrium position. Discuss whether the motion of the pendulums is periodic. (c) Graph u1(t) and u2(t) in the u1u2-plane as parametric equations. The curve defined by these parametric equations is called a Lissajous curve. (d) The positions of the masses at t 0 are given in Figure 7.6.5(a). Note that we have used 1 radian 57.3. Use a calculator or a table application in a CAS to construct a table of values of the angles u1 and u2 for t 1, 2, . . . , 10 s. Then plot the positions of the two masses at these times. (e) Use a CAS to find the first time that u1(t) u2(t) and compute the corresponding angular value. Plot the positions of the two masses at these times. (f) Utilize the CAS to draw appropriate lines to simulate the pendulum rods, as in Figure 7.6.5. Use the animation capability of your CAS to make a movie of the motion of the double pendulum from t 0 to t 10 using a time increment of 0.1. [Hint: Express the coordinates (x1(t), y1(t)) and (x2(t), y2(t)) of the masses m1 and m2, respectively, in terms of u1(t) and u2(t).]
From the textbook chapter Systems of Linear Differential Equations you will find a few key concepts needed to solve this.
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