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Re: [Phys-L] apparent weight



Yes, and I learned many new things! Maybe so much that I might not ask
this question
to my HS students! Seems a bit advanced for them. The S-E-M interactions
are complex.
We do calculate the forces of the Sun and Moon on the Earth. The Sun's
force is 175x
more, but the Moon's tidal force is 3x more. Kids wonder about this. We
also calculate
the forces of the Sun and Earth on the Moon. The Sun's force is 2x more,
yet the Moon
"appears" to orbit the Earth. It actually orbits the Sun more! Kids wonder
about this, too.


Phys-L@Phys-L.org writes:
The thread on the semi diurnal variability of g raised by Anthony was
quite animated. It needs only a mention of the twice daily change of
force per mass: corresponding to about 10 mg for a 100 kg mass - a
little beyond the resolution offered by the usual scale.

Brian Whatcott Altus OK

On 12/10/2014 10:11 AM, David Bowman wrote:
A) Any possible solar tidal effect will be essentially the same at
midnight as at noon (to leading order in the multipole expansion, i.e.
ignoring higher order multiple effects). Any diurnal solar tidal
discrepancy will be maximum between either midnight/midday and either
sunrise/sunset.
B) The lunar tidal effect is about 2.5 times stronger than the solar
one.

David Bowman

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@www.phys-l.org] On Behalf Of
Anthony Lapinski
Sent: Wednesday, December 10, 2014 8:04 AM
To: phys-l@phys-l.org
Subject: [Phys-L] apparent weight

If you stand on a sensitive scale, will you be slightly lighter at noon
(with the Sun above you and pulling opposite to Earth's gravity), and
slightly heavier at midnight (with the Sun below you and pulling in the
same direction as Earth's gravity)? Ignore any lunar effects.

This came up the other day, and nobody could really agree. One side
said no because the Earth is in freefall around the Sun, and it is the
Earth that pulls us to it. The other side said yes due to tidal effects
as seen in the oceans.

I searched online, and found the same conflicting arguments!

Can anyone help with this?

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_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l