Re: Apparent weight

[Leigh Palmer <palmer@sfu.ca>]

At 7:18 AM -0800 2/15/98, Rick Tarara wrote:
> For me, the justification for dealing the 'apparent' weight is that it helps
> us deal with a whole range of _perceived_ forces--internally experienced by
> people.  We tend to interpret many forces _backwards_ and if we keep weight
> as the 'downward' pull of the earth (or other large body) then weight is
> also one of these backwards forces.  The apparent weight is then the force
> that we perceive (to be our weight).  To be sure, in _most_ cases, this is
> what the bathroom scale reads, but what the bathroom scale reads is an
> UPWARDS force.  Don't tell me that isn't going to be confusing to students
> for whom weight has been _defined_ as what the bathroom scale reads but for
> whom the 'sensation' is downward.  Apparent weight is an attempt to deal
> with this discrepency--perhaps not successfully for some, but it works for
> me.  ;-)

The reading on *my* bathroom scale is, not surprisingly, a
scalar. If I want my weight, I multiply that number by a unit
vector pointing to my local "down", defined by a plumb bob.

What do you mean by asserting that your bathroom scale reads
an upward force? Do I have a serious conceptual lacuna here?

Just discard the word "apparent". It is about as helpful in
explaining what weight is as the word "fictitious" when it is
applied to the centrifugal force. Both weight and centrifugal
force have equivalent reality, and I assure you that your
students can recognize the kinship of these forces.

Einstein freed us from the need to observe two kinds of
forces which act on inertial masses. Why has it taken so long
to convince physicists that he has done so? We don't live in
an inertial frame of reference, and students instinctively
know how to cope with that. Why do we insist on complicating
their lives by telling them that some things they perceive
with their senses are real, and some are fictitious, but only
an ordained member of the faculty can tell them which is
which?

Leigh