Date post: | 19-Jan-2018 |
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Phases of the Moon
• Half of the moon is always illuminated
• Half of the moon is always illuminated
• We see all, none, or some of that illumination
The same side of the moon always faces the Earth.
The same side of the moon always faces the Earth.
The same side of the moon always faces the Earth.
Time for onerotation
(axis)
Time for oneorbit
(Earth)=
• Half of the moon is always illuminated
• We see all, none, or some of that illumination
• Half of the moon is always illuminated
• We see all, none, or some of that illumination- But it’s not always the same half!
p2 = ________G(MEarth)
a34π2
p: period (time for Moon to go around Earth)
a: Moon-Earth distance
Take home #1:If M becomes 0.5M,
what is the new value of p?
A few notes for the take home...
p2 = ___MEarth
C
A few notes for the in-lab...
A few notes for the in-lab...
A few notes for the in-lab...
A few notes for the in-lab...
A few notes for the in-lab...
A few notes for the in-lab...
A few notes for the in-lab...
p2 = a3
p: period in Earth yearsfor one orbit around the Sun
a: distance in AUfrom the planet to the Sun
p2 = ________4π2
G(M1+M2)a3
G = gravitational constant = 6.67 x 10-11 m3/kg/s2
MSun = 1.99 x 1030 kg MPlanet << MSun
p2 = ________G(MSun)
a34π2
________G(MSun)
4π2= 1seconds years
meters AU
F = _______GM1M2
d2
M1= Earth’s massM2 = Moon’s massd = distance between Earth and Moon
F = force that the Moon feels as it orbits the Earth
If d stays the same, what happens to Fif Earth’s mass decreases?
p2 = ________4π2
G(M1+M2)a3
G = gravitational constant = 1.475 x 10-34 AU3/kg/day2
MEarth = 5.97 x 1024 kg
MMoon = 7.36 x 1022 kg
p = period in days of the Moon’s orbit around Eartha = distance in AU between Moon and Earth
400,000km x _____________1 AU150,000,000km
= .002667 AUa =