Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: vector components and notation



Thanks for bring us back on track! Actually, the reason why I try to emphasize
components and projections is exactly because of the the sin(theta) - cos(theta)
confusion. It's not only students - I've been there myself. I encourage my
students to ONLY use cos(theta) - that is, only use projections through an
adjacent angle - which means they must find the angle to all the relevant axes.
This is a big help when they jump to 3 dimensional problems, where sin(theta)
has no meaning because it is not projecting onto any of the three axes.

We've probably all assigned the problem where students are asked to find the
angles between the vector 5i + 2j -3k and the three coordinate axes. They
dutifully take cos for the x axis, sin for the y axis and then just stare at the
paper with nowhere to go for the z axis because they don't have third trig
function. I've had some try tan(theta) :-)

Bob at PC


Rick Tarara wrote:

Hey guys (and silent gals),

Understand that most of the quibbling over vectors, component vectors, basis
vectors, projections of vectors, etc. is meaningless to 99% of our students.
They are sufficiently confused over whether the x-component is Asin(theta)
or Acos(theta). It's of course best to be consistent and 'correct', but
getting anal over it won't really help most students. ;-)

Rick

*********************************************************
Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, Indiana
rtarara@saintmarys.edu
********************************************************
Free Physics Educational Software (Win & Mac)
www.saintmarys.edu/~rtarara/software.html
NEW: Mac versions of Lab Simulations
********************************************************