![Page 1: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/1.jpg)
1
a little physics
SESAME Astronomy Winter 2011week 2
![Page 2: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/2.jpg)
2
helpful concepts
mass
gravity
angular momentum
atoms
heat/energy/temperature
![Page 3: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/3.jpg)
3
mass
“stuff”
matter
inertia
![Page 4: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/4.jpg)
4
Gravityforce between 2 objects with mass
always attractive
increases with increasing mass
decreases with increasing distance between objects
Force of gravity = a constant x(distance between objects)2
(mass of object 1) x (mass of object 2)
![Page 5: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/5.jpg)
5
Gravity is responsible for...Keeping us grounded
Keeping the moon in its orbit around Earth
Keeping the planets (and asteroids) in their orbit around the sun
Keeping the sun in its orbit around the Milky Way
making comets fall in toward inner solar system
making gas clouds collapse into stars and planets
Putting Andromeda and the Milky Way on a collision course
Making us fall into the local Supercluster
creating the anisotropies in the cosmic microwave background
keeping stars together so they can burn (instead of blowing apart from their heat
![Page 6: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/6.jpg)
6
![Page 7: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/7.jpg)
7
(see ch 5 cannon ball applet)
![Page 8: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/8.jpg)
8
angular momentum
moment of inertia x angular speed (how fast it’s turning)
it’s conserved
big and spinning slowly = small and spinning quickly
![Page 9: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/9.jpg)
9
atoms
building blocks of matter
smallest unit of an element that still has properties of that elements
made of protons, neutrons, and electrons
![Page 10: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/10.jpg)
10
atomsdifferent elements have different numbers of protons (and neutrons, and electrons)
1 atomic mass unit (amu) = mass of 1 proton (or neutron)
ignore electron’s mass (1/1700 amu)
![Page 11: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/11.jpg)
11
atomsprotons -> positive charge
neutrons -> no charge
electrons -> negative charge
nucleus (center)
protons and neutrons
where most of mass is
![Page 12: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/12.jpg)
12
energyKinetic energy
energy of motion
1/2 x mass x (speed)2
1/2 m v2
Potential energy
•has the potential to have kinetic energy
equation depends on what’s generating PE
gravitational PE on surface of Earth: mass x constant x height
general gravitiational PE:
(sigh)
(mass of object 1) x (mass of object 2)distance between objects
PE = a constant x
![Page 13: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/13.jpg)
13
energy
imagine a bowling ball and a golf ball moving at the same speed. which one has higher kinetic energy?
imagine a bowling ball and a golf ball with the same kinetic energy. which one is moving faster?
![Page 14: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/14.jpg)
14
energy
imagine a Hydrogen atom (1 proton, 0 neutrons) and a Carbon atom (6 protons, 6 neutrons) at the same temperature. which one is moving faster?
![Page 15: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/15.jpg)
15
energy
conserved (KE + PE = constant)
Example: sun and planet
1/2 mplanet v2 + G (msun mplanet)/d = constant
![Page 16: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/16.jpg)
16
energy + atoms = temperature
Temperature = Kinetic Energy of atoms
comparisons:
at a given T, are more massive atoms are moving faster or slower?
![Page 17: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/17.jpg)
17
energy + atoms + gravity + angular momentum
= Solar System formation
imagine a gas cloud (mostly Hydrogen, some Helium, a little Carbon, Oxygen, Nitrogen, Iron...)
it’s rotating slightly
gravity pulls the atoms in - makes it collapse
as the cloud contracts,
as atoms move , temperature
Yay!what happens to the speed of
its atoms?the atoms move faster
faster increases
![Page 18: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/18.jpg)
18
energy + atoms + gravity + angular momentum
= Solar System formation
some of the atoms stick together - now they have more mass, so they attract more atoms, which gives them more mass, and planets form
the center of the cloud is the densest hottest part, and it gets so hot that fusion starts in the center - a star is born!
we’ll get to fusion when we cover stars, or at least, the sun
![Page 19: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/19.jpg)
19
energy + atoms + gravity + angular momentum
= Solar System formation
closer than a certain distance, just inside the orbit of Jupiter, the temperature is relatively high, so light elements (Hydrogen and Helium) can escape
same T, lower, mass -> higher speed (in fact, escape speed) -> rocky (terrestrial) planets
Farther out, the light elements can’t escape/evaporate, so they get accreted onto the planets -> gas (jovian) planets
smaller rocky planets in inner Solar System, larger gas planets in outer Solar System
![Page 20: 1 a little physics SESAME Astronomy Winter 2011 week 2](https://reader036.vdocuments.us/reader036/viewer/2022062409/56649d785503460f94a5a8b2/html5/thumbnails/20.jpg)
20
ch 9collapse of solar nebula (with and without skater),formation of protoplanetary diskwhy does the disk flattenaccretion and formation of planets,condensate regionscomparative planetology
ch 8: kepler_3_orbit...htm