Transcript c5011_x4_Chabay

Computing in the introductory physics course
Ruth Chabay and Bruce Sherwood
North Carolina State University
VPython
3D programming for ordinary mortals
Programming language (Python)
Easy to learn
Vector computations
Navigable 3D animations are a side effect
Object-oriented
Free, open source, runs on all platforms
http://vpython.org
Student program to
compute and
display the motion
of a proton in a
cyclotron. The
orange arrow
represents the
electric field in the
gap at this instant.
The graph displays
kinetic energy of the
proton vs. time.
Student program to
compute and
display the motion
of a 3D massspring system.
The Newtonian synthesis
The momentum principle + force law + initial conditions
Iterative update of momentum and position, for two or
more interacting objects
Student program to
compute and display
the motion of a
proton in a uniform
magnetic field.
Arrows represent
momentum and
magnetic force.
Simple Euler algorithm is quite adequate: computers are
fast, so step size can be decreased if behavior is erratic.
Student program to compute and display the
motion of a spacecraft near a fixed Earth and
Moon. The green arrow represents momentum.
Vector algebra  VPython code
Student program to
calculate and display the
electric field due to a
uniformly charged rod at
various locations. The rod
is approximated by a
number of discrete point
charges; students vary the
number of charges, and
study the effect on their
computed results.
Student program to compute and display the
magnetic field of a moving proton at many
locations, dynamically.
Programs written by students
include (Intro course, 2 semesters):
Student program to compute and display the trajectory of an alpha particle
scattering off a gold nucleus, and to plot x and y components of the
momentum of each object vs. time. (In the program the gold nucleus does
recoil, but it has not moved far enough to leave a visible trail.) The basic
algorithm for Rutherford scattering, spacecraft orbits, and the 3D massspring system is the same; only the force law changes.
Motion of a fancart (constant force)
Spacecraft orbit
Spacecraft orbit with energy graphs
3D Mass-spring
3D Mass-spring with energy graphs
Rutherford scattering with momentum graphs
Statistical mechanics of Einstein solid
Electric field of point charge
Electric field of dipole
Electric field of uniformly charged rod
Magnetic field of moving proton
Charge motion in uniform magnetic field
Positron motion in electromagnetic plane wave
New features in VPython (beta):
transparency, textures, lighting
Lecture demo
program
illustrating the
electric field on a
transparent
Gaussian surface.
Matter & Interactions
Modern calculus-based introductory physics course
20th century physics integrated throughout both semesters
Computation integrated to strengthen conceptual understanding,
aid visualization
R. Chabay & B. Sherwood, John Wiley & Sons, 2002, 2005
http://www4.ncsu.edu/~rwchabay/mi
These new features in
VPython were added by
Jonathan Brandmeyer.
The development of VPython and
Matter & Interactions has been
supported in part by the National
Science Foundation. VPython was
originated by David Scherer.