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: [Phys-l] ? passive force of constraint





This might be overly obvious to the experts on this list. My apologies if this is so.

For physics beginners (which is my teaching audience), I've found it helpful for students to:
1-draw a sketch before they attempt a fbd. Sometimes 2 sketches so we can look @ motion b4 & after the interaction.
2-Circle thejavascript:SetCmd(cmdSend);
Send object of interest in the sketch.
3-Anywhere the object is in contact w/anything, there must be an interaction.
---Each contact results in 1 force being added to the diagram.
4-students look for field forces. Add field forces to the fbd as needed.

It works for me. I found the method in Alan Van Heuvelen's ALPS (active learning problem set (sheets?)). Similar methods are discussed by Heller at the U of MN and in Alan Van Heuvelen's Overview Case Study Physics methods.


The previous posts moral is so rhythmic it comes dangerously close to creating complete recall of the Mr. Ed theme song.




Paul Lulai
Physics Teacher
St. Anthony Village Senior High
Saint Anthony Village, MN
55418
(w) 612-706-1144
(fax) 612-706-1020
plulai@stanthony.k12.mn.us



-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu on behalf of Jack Uretsky
Sent: Thu 7/19/2007 7:55 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] ? passive force of constraint

Hi all-
I think that some exercises with free-body diagrams can help
students rid themselve of the spurious distinction between active and
passive forces. In Scott's example, one can start with pictures of a
weight being held up by a weightlifter, and a seight resting on a flat
surface. Now, in each case, have the student draw a free-body diagram of
the weight. If the diagrams are different, some careful leading questions
can be used to lead the student to making the diagrams identical.
Moral: as already pointed out, a force is a force is a force.
Regards,
Jack