Lecture: Applications. Damped and undamped motion.Last time: Theory of equations and 5.3-32. Problems discussed in class: 5.4-20,34 Spring-mass equation, LRC-circuit equation, Spring-mass DE and RLC-circuit DE derivations. Electrical-mechanical analogy. The RLC circuit equation and its physical parameters. Spring-mass equation mx''+cx'+kx=0 and its physical parameters. Forced systems. Forcing terms in mechanical systems. Speed bumps. Forcing terms in electrical systems. Battery. Generator. Harmonic oscillations: sine and cosine terms of frequency omega. Damped and undamped equations. Phase-amplitude form. Damped oscillations overdamped, critically damped, underdamped [Chapter 5] phase-amplitude form of the solution [chapter 5] Undamped oscillations. Harmonic oscillator. Partly solved 5.4-20. See the FAQ at the web site for answers and details. Class notes transcribed the wrong coefficients. Corrected in FAQ. Partly solved 5.4-34. The DE is 3.125 x'' + cx' + kx=0. The characteristic equation is 3.125r^2 + cr + kr=0 which factors into 3.125(r-a-ib)(r-a+ib)=0 having complex roots a+ib, a-ib. Problems 32, 33 find the numbers a, b from the given information. This is an inverse problem, one in which experimental data is used to discover the differential equation model. The book uses its own notation for the symbols a,b: a ==> -p and b ==> omega1. Because the two roots a+ib, a-ib determine the quadratic equation, then c and k are known in terms of symbols a,b. See also the web site FAQ for more details.

- References: Sections 5.4, 5.6. Forced oscillations.

Slides on Section 5.4Beats. Decomposition of x(t) into two harmonic oscillations of different natural frequencies. Envelope curves. Sound waves. Pure resonance. Pendulum. Cafe door. Pet door. Over-damped, Critically-damped and Under-damped behavior. pseudoperiod. Shock-less auto. Rolling wheel on a spring. Bike trailer. Physical pendulum. Washing machine. Swinging rod. Mechanical watch.

Drilltop=x-1, bot=(x+1)(x^2+4) top/bot = A/(x+1)+(Bx+C)/(x^2+4); find A,B,C. Sampling in partial fractions. Method of atoms in partial fractions. Heaviside's coverup method. Solution to 4.7-10: Subspace Criterion. Blackboard only.Lecture: Basic Laplace theory.Reading: Chapter 10. Read 5.5, 5.6, ch6, ch7, ch8, ch9 later. Direct Laplace transform == Laplace integral. Def: Direct Laplace transform == Laplace integral == int(f(t)exp(-st),t=0..infinity) == L(f(t)). Introduction to Laplace's method. The method of quadrature for higher order equations and systems. Calculus for chapter one quadrature versus the Laplace calculus. The Laplace integrator dx=exp(-st)dt. The Laplace integral abbreviation L(f(t)) for the Laplace integral of f(t). Lerch's cancelation law and the fundamental theorem of calculus. A Brief Laplace Table 1, t, t^2, t^n, exp(at), cos(bt), sin(bt)

A brief Laplace table. Forward table. Backward table. Extensions of the Table. Laplace rules. Linearity. The s-differentiation theorem (d/ds)L(f(t))=L((-t)f(t)). Shift theorem. Parts theorem. Finding Laplace integrals using Laplace calculus. Solving differential equations by Laplace's method.Basic Theorems of Laplace TheoryLerch's theorem Linearity. The s-differentiation theorem (d/ds)L(f(t))=L((-t)f(t)). Shift theorem L(exp(at)f(t)) = L(f(t))|s->(s-a) Parts theorem L(y')=sL(y)-y(0)