This first half of the course, dealing with ordinary differential equations (ODEs), is taught by Prof. Matthias Heil. The second half, dealing with mechanics, is taught by Dr. Rich Hewitt who provides a separate page for his course notes. This page provides online access to the lecture notes, example sheets and other handouts and announcements. Most of the material will be taught in "chalk and talk" mode. If OHP transparencies are used, copies will be made available (after the lecture) on this page.
Please note that the lecture notes only summarise the main results and will generally be handed out after the material has been covered in the lecture. You are expected take notes during the classes.
The Riot Act -- Please Read
The supervisions are for YOUR benefit -- if you have any problems with the material, YOU have to take the initiative and raise them during your supervision class. You will be expected to have at least tried to solve the problem so that you are in a position to ask specific questions. Most of the problems are extensions/modifications of examples presented in class, so it's a good idea to have a look through your lecture notes before attempting the questions on the example sheets. The following exchange tends to take place at the beginning of most of my lecture courses:
Student: "I can't do that question"
To be absolutely clear: If you can't do a question even though you've tried really hard [see below for a definition of "really hard"], and you have consulted all the available material, I'll be delighted to help you -- that's my job, after all. However, if you expect me (or my colleagues) to turn supervisions into repeat performances of the lectures because attending them would interfere too much with your social life, or if you can't be bothered to read the handouts, I will have very little sympathy.
I will distribute detailed solutions (again in pdf format on this page) after the material has been covered in the supervisions but these should only be used to check your solutions. Do not make the mistake of assuming that it'll be sufficient to look at somebody else's solution to understand the material! "Maths is not a spectator sport!".
While I'm having a general rant, let me address another frequently-asked-question:
|Date||Topics covered||Do-able questions|
|Week 1||We haven't done anything yet! However, tutorials will already take place during week 1 and some of you may have your first tutorial before the first lecture. Don't panic: The "warm up" exercises on Example Sheet 0 should all be do-able, provided you remember your A-Level maths and have your brain switched on....||Example sheet 0 (all questions!)|
||Introduction; notation; classification (order, linearity; autonomous ODEs); examples of ODEs and solutions; motivation for existence and uniqueness; counter-example for existence; uniqueness and boundary/initial conditions; number of constraints related to order of ODE; formal definition for IC/BC and IVP/BVP; example for IVP (1D motion of a particle subject to a prescribed force); example for BVP (transverse deflection of a string under constant tension).||Example sheet 1 (all questions!)|
||Counterexample for uniqueness. "Proper" theory: Existence and uniqueness for first-order nonlinear ODEs; examples. Existence and uniqueness for linear first-order ODEs; examples. Graphical solutions for first-order ODEs: The direction field; integral curves. Graphical explanation for how non-uniqueness may arise at points where f(x,y) is discontinuous. Asymptotes, stability of solutions. Isoclines. Sketch solution curves for y'=-x/y and infer that solutions are arcs of circles.||Example sheet 2: Q1(a-b)|
||Further discussion of y'=-x/y: a unique solution exists for most initial values, but only for a limited range of x values. Definition of critical points. Separable ODEs; two ways of incorporating initial conditions; examples. ODEs of homogeneous type; examples. First-order linear ODEs: Integrating factor. Example.||Example sheet 2: All questions.|
||Revisit integrating factor example. Observation: The solution of a linear ODE can be written as the sum of a particular solution of the full equation and the general solution of the homogenous ODE. Marvel at this for a while. 2nd-order ODEs. General statement of IVPs and BVPs. Specific theory for 2nd-order linear ODEs: Existence and uniqueness; the homogeneous ODE and the superposition of its solutions; linear (in)dependence of functions; fundamental solutions for homogeneous ODEs (they're not unique!); the general solution of the inhomogeneous ODE. Example; demonstrate that choosing different particular solutions and different fundamental solutions in the general solution does not change the solution of the IVP.||Example sheet 3: Q1&2.|
||Illustration that the structure of the general solution, x = x_P + x_H, occurs in many other contexts such as linear algebra. Summary of the solution procedure for linear ODEs: Fundamental solution of the homogeneous ODE; particular solution of the inhomogeneous ODE; the sum yields the general solution; BC/IC determine the arbitrary constants in the fundamental solution. Constant coefficient ODEs: exp(lambda x) for homogenous solutions: 3 cases: distinct real roots; repeated root; complex conjugate roots. Examples. Particlar solutions for constant-coefficient ODEs: The method of undetermined coefficients as a trial-and-error-method, guided by the form of the RHS. Start to examine the method and its pitfalls for exponential forcing.||Example sheet 3: All questions.|
||Identification "pathological" cases for exponential RHS and interpret them in terms of roots of the characteristic polynomial and (alternatively) as cases in which the RHS is a solution of the homogeneous ODE. Generalise to arbitrary RHSs consisting of multiple, linear independent functions. Generalise to the case with multiple, linearly independent RHS of general form, including the modifications required (i) if derivatives of functions on the RHS create new, linearly independent functions when differentiated and (ii) if one of the functions on the RHS is a solution of the homogeneous ODE.||Example sheet 4: Q1a,b,c and Q2.|
||Examples for method of undetermined coefficients, covering all special cases. Nonlinear 2nd order ODEs of special type: 2nd order ODEs that don't contain the dependent variable y''=f(x,y'). Autonomous ODEs y''=f(y,y'). Examples for both cases.||Example sheet 4: Everything.|
||Start "mechanics applications of second-order ODEs". Perform experiment with mechanical oscillator (mug on rubber string). Discuss Newton's law in detail and derive the governing equations for mass-spring system (OHPs). Derive equations for mass-spring-damper system on board. Interpretation of the four types of solutions of the homogeneous equation (pure damping; critical damping; damped oscillations; undamped oscillations). Interpretation of delta and omega as timescales for the decay of the oscillation and timescale of the undamped oscillations, respectively. Particular solution for harmonic forcing. Dependence of the amplitude of the response on various parameters (and their ratios!). Quasi-steady limit; high-frequency limit; large amplitudes for excitation near eigenfrequency.||Example sheet 5: Questions 1 (or 0) and 2.|
||Finish off harmonic oscillator example: Resonance for delta=0 (mathematical symptom: forcing function is solution of the homogeneous ODE). Amplitude grows linearly. Motivation for perturbation methods: Forced mechanical oscillator with small forcing frequency. Argue heuristically that for Omega << 1, it should be possible to approximate the ODE m x'' + k x' + c x = F cos(Omega t) by c x = F cos(Omega t). Verify by examining the limit of the exact solution for small Omega. Algebraic example (roots of a second order polynomial) to illustrate the overall structure of perturbation expansions. Start ODE example involving IVP corresponding to mechanical oscillator with weak damping. Write down expansion for solution.||Example sheet 5: All questions. Example Sheet 6: Question 1.|
||Derive sequence of IVPs for weakly damped oscillator. Solve sequence of IVPs and show how they provide an increasingly accurate representation of the exact solution as more and more terms are added to the expansion. Compare against exact solution. Highlight features: Including more terms into the expansion increases accuracy at fixed time but ultimately all perturbation solutions diverge. Reason for divergence: Superficially: terms proportional to powers of t in the solutions; more deeply: errors in the ODE accumulate. Start nonlinear example: Derive equations for nonlinear pendulum. Discuss existence and uniqueness for nonlinear pendulum.||Example Sheet 6: Question 2.|
||Do perturbation expansion for small initial amplitudes. Key feature: Length of period increases with size of initial amplitude. This is captured by the perturbation expansion.||Example sheet 6: All questions.|
Tuesday 12th March 2013 17.15-18.15 in Renold Lecture Theatres C2, C9 and C16
The test is a "closed book", multiple-choice test -- no notes are allowed. Please take some form of ID (ideally your library card) with you.
The test will be returned via the supervision groups (at least for those of you who followed the instructions and provided the name of your supervisor on the answer sheet). Note that there were four different versions of the test, all containing the same questions but in different order. The model solution for version V1 is available as a pdf file. If you kept the question sheet with your working, you should be able to reconstruct which question is which. (If you didn't, then what's the point looking at the solution?)
Rich Hewitt is likely to ask you to do some coursework (worth another 5%), too.
Please note a few corrections for previous handouts (the files above have already been corrected).