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] bound vectors ... or not



I'm saying if I tie Rope B to a Object A, the force F(on A due to B)
*is* applied to a specific point (or can at least be integrated to one
effective point).

The vector we use to describe the magnitude and direction of the force
is not "localized' or physically bound anywhere. That same vector could
be used to describe the magnitude and direction of any number of other
forces (perhaps the force of you pushing on the other side).

These two forces are different forces with the SAME magnitude and
direction. As such they produce the same result -- the same
acceleration (when applied independently)-- but they are not the "same
force". To do vector addition, I can move the vectors around wherever I
want (but that doesn't move where the rope is tied).

Is kind of like the $1 bill in my pocket and the $1 bill in your pocket
have the same value, but they are not the "same $1 bill".

Tim Folkerts


-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Herbert
Schulz
Sent: Tuesday, September 07, 2010 7:50 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] bound vectors ... or not


On Sep 7, 2010, at 7:41 AM, Folkerts, Timothy J wrote:

It seems that "bound vector" relates to a "specific force"
and "free vector" relates to a "general force".

If I talk about F(AB) = the force on "A" due to "B", then I am talking
about a push with a specific magnitude and a specific direction AND
located at a specific point on "A" (assuming a "point force" for
simplicity).

As far as solving the equations of motion, this is an over-specified
condition. Any OTHER force of the same magnitude and direction would
cause the same acceleration of "A". It doesn't need to be this
specific
F(AB) (ie "bound vector"). It could any other similar force (ie free
vector).


So F(net) = ma works for ANY (free) vector, and it works in particular
for this specific (bound) vector F(AB).


Just my $0.02 ....

Tim Folkerts

Howdy,

Are you meaning to say that those vectors are physically attached to the
point? I can't ``move'' the vectors so they are tail to head to get the
sum of the vectors?

I'm not getting the concept of a ``bound vector'' at all.

Good Luck,

Herb Schulz
(herbs at wideopenwest dot com)



_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l