Physics 43 (Dynamics) Home Page, Fall 2008

Physics 43: Dynamics

Announcements

Welcome to the new semester!

Instructor

Course Information

Course Catalog Description:

This course begins with the foundation of classical mechanics as formulated in Newton's Laws of Motion. We then use Hamilton's Principle of Least Action to arrive at an alternative formulation of mechanics in which the equations of motion are derived from energies rather than forces. This Lagrangian formulation has many virtues, among them a deeper insight into the connection between symmetries and conservation laws. From the Lagrangian formulation we will move to the Hamiltonian formulation and the discussion of dynamics in phase space, exploring various avenues for the transition from the classical to the quantum theory. We will study motion in a central force field, the derivation of Kepler's laws of planetary motion from Newton's law of gravity two-body collisions, and physics in non-inertial reference frames. Other topics may include the dynamics of driven, damped oscillators, and non-linear dynamics of chaotic systems. Three class hours per week. Requisite: Physics 27 or consent of the instructor.

Schedule

Times and places:

Requisites

Physics 27 or consent of the instructor

Course requirements

Statement of Intellectual Responsibility: particulars for this course

How to get the most from this class:

Grading:

Textbooks:

Required (I've confirmed that it is available at the Jeffrey Amherst bookstore): Additional useful references:

On mechanics in general: Math books:

Mathematica Tutorials

We will use Mathematica fairly extensively in the homework, to obtain numerical solutions to problems that are not analytically solvable and to simplify plotting of results. If you've never used Mathematica before, or haven't used it much, the tutorials will help you get started. They were written by Professor Emeritus Bob Hilborn and revised by Rebecca Erwin '02. If you download the file and save it to the desktop with a .nb suffix in the name, your computer will recognize it as a Mathematica notebook and will start up Mathematica automatically when you double-click on the icon, provided you have Mathematica installed. Mathematica is installed on lots of the college's public machines, including on the computers in the Physics Department computer lab. Alternately, you can pay the $140 or so to buy the student version.


Lecture Schedule
Week Notes Hmwk Other
1. September 1
Space, Time, and Newton's Laws / Vectors


Sept 2: Intro and Logistics / Space, time, and vectors

Scope of classical mechanics, and scope of the course. Space and time: the background manifold we'll use. Geometrical vectors: define vectors as quantities that transform under rotations as the displacement.

[Handouts: Student information sheet ]

Sept 4: More about vectors

Write general vectors in terms of orthonormal basis vectors. Einstein summation convention. In 2D, compare, contrast, and convert between Cartesian and polar basis vectors. Products of vectors and the geometrical interpretation: scalar and vector products. Levi-Civita symbol and Kronecker delta. Differentiation of vector functions: definition, versions of familiar calculus rules. Beware: basis vectors in non-cartesian coordinates have non-trivial derivatives!

[Handouts: Vector analysis with diagrams (pp. 7-11 of Stedman's Diagrammatic Methods in Group Theory)]

Read: Kibble, Chap. 1 and Appendix A

Problems: [Due Tuesday 9/9/08, 11:59 pm]
Chap. 1: 7, 8, 10
Appendix A: 7
Chap. 2: 3, 7
2. September 8
Vectors / Newton's Laws / Linear Motion


Sept 9: Vectors / Newton's Laws

Differentiation of vectors: position, velocity, and acceleration in polar coordinates. Diagrammatic argument that derivatives of radial and polar vectors "make sense." Interpretation of terms in expression for acceleration vector. Finite rotations are not vectors (infinitesimal rotations are).

Reference frames defined (inertial frames particularly important). Mass and force defined rather casually.

Newton I addresses natural state of motion, serves to define inertial frames. Newton II is the "workhorse." Newton III (strong form and weak form). Consequence of Newton III: conservation of linear momentum for composite systems. Failures of NIII (in relativity, in electrodynamics).

Linear motion: conservative forces and energy conservation.

Sept 11: Linear Motion

Conservative forces and conservation of energy: When F=F(x), can always find a first integral of motion (fn of x and v) which is constant in time. Show that T+V=E is constant in time. Show how the potential energy landscape can be used to give qualitative description of motion evey without explicit solution (stable and unstable equilibria, turning points).

Small oscillations about equilibrium: Taylor expand about equilibrium point. Only second order and higher terms in small displacement are nonzero. If equilibrium is stable, displacements may remain small for all time; not so if unstable. In stable equilibrium, leading term is usually quadratic: harmonic oscillator potential.

Harmonic oscillator potential: possible motions for SHO and inverted SHO potentials. Equation of motion. 2nd order linear ODE--general solution has two linearly independent terms and two constants of integration. Linear ODEs satisfy superposition principle. Show that superposition of solutions is also a solution for linear equations, and that it's not true in general for nonlinear equations. Guess solutions of exponential form, solve.

Read: Kibble, Chap. 2

Problems: Kibble, Chap. 2: 8, 9, 15, 20, 26, 30
3. September 15
Energy and Angular Momentum


Sept 16: Title



Sept 18: Title



Read:

Problems:
4. September 22
Central Conservative Forces


Sept 23: Title



Sept 25: Title



Read:

Problems:
5. September 29
Noninertial reference frames


Sept 30: Title

Oct 1: Exam 1 (7-9 pm)

Oct 2: Title



Read:

Problems:
6. October 6
Potential theory


Oct 7: Title

Oct 9: Title

Read:

Problems:
Exam practice: P43F04 exam 1
7. October 13
Two-body and Many-body problems


Oct 14: Fall Break



Oct 16: Title



Read:

Problems:
8. October 20
Rigid body motion


Oct 21: Title



Oct 23: Title



Read:

Problems:
9. October 27
Lagrangian mechanics


Oct 28: Title



Oct 30: Title



Read:

Problems:
10. November 3
Small oscillations and normal models


Nov 4: Title

Nov 6: Title



Read:

Problems:
11. November 10
Hamiltonian mechanics


Nov 11: Title

Nov 13: Title



Read:

Problems:
Exam practice: P43F04 exam 2
12. November 17
Geometry of dynamical systems


Nov 18: Title

Nov 19 (evening): Exam 2

Nov 20: Title



Read:

Problems:

13. December 1
Chaos in Hamiltonian systems


Dec 2: Title

Dec 4: Title



Read:

Problems:
14. December 8
Geometric mechanics


Dec 9:

Dec 11: Reading period



Read:

Problems: