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-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@www.phys-l.org] On Behalf Of John
Clement
Sent: Thursday, December 11, 2014 2:02 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] apparent weight
The accleration of the object closer to the Sun is greater because the
gravitational force is greater. Of course this is ignoring the rotation of the
Earth which will also have to be factored in for a more exact calculation. That
this is correct is easily seen by the tides. At noon the water is rising because
the pull of the Sun/mass is greater on the water which is closer to the sun
than the Earth underneath. Again this is a simple model which should appeal
to a beginning physics student and ignores complications and second order
effects. The tidal forces are certainly complicated by geography and the
Coriolis pseudo force.
If the effect were the reverse, then when the sun and moon were at 90
degrees the tides would be greatest, but it is when they are lined up with the
Earth that you get the highest tides or what is often termed a "spring tide".
I am curious as to the reasoning you used to deduce that the effect is the
reverse of what I claim.
John M. Clement
Houston, TX
Defining the acceleration of the person as the time rate of change of
the velocity of the person relative to a reference frame in which the
sun is at rest at the origin and the earth is orbiting the origin once
per year, you have it exactly backwards. The person's acceleration is
greater than that of the center of the earth at midnight when the
person is farther from the sun, and smaller than that of the center of
the earth at noon when the person is closer to the sun.
above and the
The lighter scale reading will happen for both the Sun
Sun below, just as the Moon produces 2 tides. This simple analogytowards the
argument might be helpful with students. The simple physics
explanation is that since you are closer to the Sun when above than
the center of the Earth, you have a greater acceleration toward the
sun. When the sun is below the Earth is accelerating more
sun than you are because it is closer to the Sun. In bothcases this
results in a lower scale reading. I will leave thecomplicated explanations to others, as they will confuse most
students.
Unfortunately most simple accounts of the tides ignore thetrue effect
and just talk about the pull. It is a gradient effect.seeing this
Of course a simple bathroom scale would be inadequate for
effect, and a gym scale which is a balance would show no effect.lighter at
John M. clement
Houston, TX
If you stand on a sensitive scale, will you be slightly
below younoon (with the Sun above you and pulling opposite to Earth's
gravity), and slightly heavier at midnight (with the Sun
Ignore any lunar effects.and pulling in the same direction as Earth's gravity)?
said yes due
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
_______________________________________________to tidal effects as seen in the oceans.
I searched online, and found the same conflicting arguments!
Can anyone help with this?
_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l