UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.
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Transcript of UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.
![Page 1: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/1.jpg)
UNIVERSAL GRAVITATIONand
SATELLITE MOTION
Chapters 12 and 14
![Page 2: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/2.jpg)
Isaac Newton wanted to know why the moon travels in a circular path
around the Earth.
![Page 3: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/3.jpg)
As a student of physics, Newton knew that
any object moving in a circular path is experiencing a centripetal force
– a force directed toward the axis.
![Page 4: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/4.jpg)
He knew it had to be a centripetal force
that makes the moon travel in a circular
orbit around the Earth, as well.
But nobody knew what it actually was out there
that provides that centripetal force.
![Page 5: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/5.jpg)
Newton realized he had already studied a force that pulls on
objects and is pointed to the center
of the Earth…
GRAVITY!
![Page 6: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/6.jpg)
• Remember, Isaac Newton did not discover gravity.
• He discovered that gravity is universal.
• He recognized that the force that pulls an apple from a tree to the ground, is the same as the force that keeps the moon in orbit.
![Page 7: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/7.jpg)
The Falling Moon
• So if the Earth’s gravity pulls on the moon, why doesn’t the moon fall onto the Earth?
![Page 8: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/8.jpg)
The Falling Moon
• The same reason the rubber stopper didn’t get pulled in and hit your hand in the lab… it was moving too fast to get pulled in.
![Page 9: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/9.jpg)
The Falling Moon
![Page 10: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/10.jpg)
Think back to projectiles that are fired or launched horizontally.
![Page 11: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/11.jpg)
Imagine what would happen if the projectile were fired faster... and faster…
![Page 12: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/12.jpg)
The projectile would follow the curvature of
the Earth if it were fired fast enough.
![Page 13: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/13.jpg)
How fast would you have to throw something to put it in orbit?
Gravity pulls the object down 5 meters in the first second… so it would have to move 8 kilometers horizontally
in order to “miss” the Earth as it falls.
![Page 14: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/14.jpg)
That’s farther than the
distance from J.R. Tucker
High School to Short Pump Town Center!
![Page 15: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/15.jpg)
• Anything moving 8 km/s horizontally is moving fast enough to avoid hitting the Earth as it “falls”.
• In other words, it will be in orbit. This is how satellites stay up.
• 8 kilometers per second = 17895.5 mph… or 5 miles per second!
• http://science.nasa.gov/temp/HubbleLoc.html
![Page 16: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/16.jpg)
J-Track
• http://science.nasa.gov/Realtime/JTrack/3d/JTrack3D.html
![Page 17: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/17.jpg)
• The higher the orbit of a satellite, the less its speed and the longer its period.
• The period of orbit is the time to complete one revolution.
Orbits
![Page 18: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/18.jpg)
Orbits
- Satellites that orbit close to the Earth (altitude ~400 km) have a period of ~90 minutes. (ISS, Hubble, communications)
- Satellites that orbit at a higher altitude (~36,000 km) have a period of 24 hours – “geosynchronous” (GPS, spy satellites)
- The moon orbits at an altitude of nearly 400,000 km and its period is 27.3 days.
![Page 19: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/19.jpg)
• If a projectile is given a horizontal speed that is just slightly more than it needs to attain orbit, it will overshoot the circular path and trace an elliptical orbit.
Elliptical Orbits
![Page 20: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/20.jpg)
![Page 21: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/21.jpg)
• Remember, a satellite that is farther away orbits more slowly than one that is closer.
• For an elliptical orbit, a satellite is farther away at some times than at others. Therefore, it does not keep a constant speed.
• The satellite moves slowest when it is farthest away (apogee), and fastest when it is closest (perigee).
Elliptical Orbits
![Page 22: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/22.jpg)
Elliptical Orbits
![Page 23: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/23.jpg)
Elliptical Orbits
![Page 24: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/24.jpg)
Geography of Launches
• Where would be the easiest place to launch from, in order to achieve a horizontal speed of 8 km/s?
• Where would be the hardest place to launch from, in order to go that fast?
![Page 25: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/25.jpg)
Remember that objects with the same rotational speed can have different linear speeds if they are different distances from the axis of rotation…
![Page 26: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/26.jpg)
![Page 27: UNIVERSAL GRAVITATION and SATELLITE MOTION Chapters 12 and 14.](https://reader030.fdocuments.in/reader030/viewer/2022032709/56649ed45503460f94be4557/html5/thumbnails/27.jpg)
Geography of Launches