Gravity How come the astronauts float around when they are inside the space shuttle? A) The...
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Transcript of Gravity How come the astronauts float around when they are inside the space shuttle? A) The...
![Page 1: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/1.jpg)
Gravity
How come the astronauts float around when they are inside the space shuttle?A) The shuttle’s rockets compensate for gravityB) The shuttle is so far from earth that gravity is very, very weak.C) Earth’s atmosphere shields the shuttle from gravityD) The Moon’s gravity compensates for the Earth’sE) NASA didn’t pay the gravity billF) There is nothing holding the shuttle up
Orbits
![Page 2: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/2.jpg)
What happens when something holds you up.
Gravity pulls you downFloor pushes you up
Forces balance - you don’t go anywhere.You know which way is up because that is the way the floor is pushing you
Gravity and Orbits - Not Free Fall
Help!
•Cut the cable•The elevator starts falling•The floor no longer holds you up•You fall too•You float around – no gravity•Because you and elevator are falling at the same rate, feels like weightlessness•Free fall can be up, down, or sideways
![Page 3: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/3.jpg)
“The knack [to flying] lies in learning how to throw yourself at the ground and miss” - The Hitchhiker’s Guide to the Galaxy trilogy, in Life, the Universe, and Everything
Gravity and Orbits - Circular Orbits
2o
GMv
R
![Page 4: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/4.jpg)
Gravity and Orbits
How come the astronauts float around when they are inside the space shuttle?A) The shuttle’s rockets compensate for gravityB) The shuttle is so far from earth that gravity is very, very weak.C) The Earth’s atmosphere shields the shuttle from gravityD) The Moon’s gravity compensates for the Earth’sE) NASA didn’t pay the gravity billF) There is nothing holding the shuttle up
![Page 5: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/5.jpg)
Non-circular orbits•If velocity is more or less than this, you get an ellipse
•If velocity is big enough, it leaves on a parabola – escape velocity
2 2e
GMv
R
•If velocity is bigger, it leaves on a hyperbola
2o
GMv
R
![Page 6: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/6.jpg)
Two Body Orbits
Center of Mass•The Center of Mass is where the two masses would balance
•The objects go around each other
•How come the Sun doesn’t go around the Earth? It does!
(M + m)P2 = a3
![Page 7: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/7.jpg)
Announcements
5/28
Date Read QuizToday Sec. 4.1 – 4.4, yes
Gravity LectureMonday Sec. 5.1 yesTuesday Sec. 5.2 – 5.3 yes
Test next Thursday!Information sheet
online soon?
![Page 8: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/8.jpg)
Kepler vs. Newton
(M + m)P2 = a3
P2 = a3
Sun + Earth
M + m = 1 + .000003 1
Applies to planets around the Sun
Always applies
•Masses in Solar Masses
![Page 9: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/9.jpg)
Gravity vs. Pressure = sphere
•Gravity wants to squish everything to a point•Pressure wants it to spread out•They balance to make a sphere
•If an object rotates, it makes a flattened (oblate) sphere•Small objects can be any shape
![Page 10: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/10.jpg)
26,000 year cycle
Precession•Gravity pulls unevenly on the flattened Earth•Earth is like a top – its tilt changes over time
![Page 11: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/11.jpg)
Gravity vs. Rotation = Disk Dust or gas or chunks - disk formsRotation keeps it from falling inGravity keeps it from escaping
•Rings around Planets•Spiral Galaxies•Accretion disks•Protoplanetary disks
![Page 12: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/12.jpg)
Tidal Forces
![Page 13: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/13.jpg)
Tidal Distortion (greatly exaggerated)
![Page 14: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/14.jpg)
Big Tides Sun
Moon
Earth
Small Tides Moon
EarthSun
Spring (big) and Neap (small) Tides
![Page 15: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/15.jpg)
Tides
Generally, high tide occurs twice every day. Why?A) There are two causes of tides, the Sun and the MoonB) The Moon causes two places on the Earth’s oceans to bulge and have high tideC) The second high tide is sort of an echo of the first tideD) The Moon goes around the Earth twice every day
![Page 16: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/16.jpg)
Rotation causes bulge to be in wrong placeBulge has gravitational pull on MoonEarth rotation slowsMoon slung to higher, slower orbit
Bulges and the Earth/Moon system
Earth Moon
without rotation
Earth
Earth and Moon bulge want to alignStrong effect on the Moon
with rotation
![Page 17: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/17.jpg)
Tidal locking
Why can we only see one side of the Moon?A) Because the Sun only shines on one side of the MoonB) Because the Moon doesn’t rotate, so we never see the back side of the MoonC) The Moon rotates at the same rate as it goes around the EarthD) It is like a rainbow; it doesn’t have another side
Moon
Moon
Moo
n
Moon
Earth
![Page 18: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/18.jpg)
planet moon
Tidal HeatingChanging shape as distance changesFlexing generates heat
![Page 19: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/19.jpg)
Planet
Moon
Roche Limit
![Page 20: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/20.jpg)
Roche Limit - Rings
![Page 21: Gravity How come the astronauts float around when they are inside the space shuttle? A) The shuttle’s rockets compensate for gravity B) The shuttle is.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649e6a5503460f94b68926/html5/thumbnails/21.jpg)
Where is Titan [a very large moon of Saturn] compared to Saturn’s rings?A) It is closer than the ringsB) It is farther away than the ringsC) It is within one of the ringsD) It is between rings - there are rings both inside and outside it.
Roche Limit - Rings