satellite motion
DESCRIPTION
Satellite Motion . Curvature of Earth. The Earth’s surface drops 5 vertical meters for every 8000 meters tangent to its surface. 8000 meters. 5 meters. 8000 meters. 5 meters. How fast does an object need to go to become an Earth satellite?. How far does an object fall in 1 second? 5m - PowerPoint PPT PresentationTRANSCRIPT
Satellite Motion
Curvature of Earth8000 meters
8000 meters
5 meters
5 meters
The Earth’s surface drops 5 vertical meters for every 8000 meters tangent to its surface
How fast does an object need to go to become an Earth satellite?
• How far does an object fall in 1 second?– 5m
• How far along the horizon must you go for the Earth to curve 5m down?– 8000m
8km/s for orbital speed close to Earth!
• Does the force of gravity affect the speed of a bowling ball down an alley?– Nope!
• Similarly, the force of gravity of the Earth does not affect the speed of a satellite in circular orbit. – Why?– 90 degrees between force and direction of motion…
No Work!
Circular Orbit
The period for a satellite in low-Earth
orbit is about 90 minutes.
At which position does the satellite have its greatest speed? Why?
A
B
C
D
Same speed Everywhere along path!
A close Earth satellite has a
period of about 90 minutes.
• What if an object above the atmosphere has a horizontal speed of more than 8km/s?– Its path is that of an ellipse
instead a circle.
• Most satellites actually have elliptical paths!
• Speed varies in elliptical orbit
Kepler’s 1st Law of Planetary Motion
Johannes Kepler
Ellipse
• Foci- Where the main body of an orbiting pair lies
At which position does the satellite have its greatest speed? Why?
A
B
C
D
Greatest Speed
Lowest Speed
Kepler’s 2nd Law of Planetary Motion
Faster closer to other source of gravity
Slower when far away
Equal areas swept out over same amounts of time time!
Apogee- when satellite is at farthest position
Perigee- when object is at closest position
Energy Conservation and Satellite Motion
The sum of potential and kinetic energies of
a satellite remains constant
KE+PE
KE+PE
KE+PE
KE+PE
KE+PE
KE+PE
KE+PE
KE+PE
“What goes up must come down”or does it???
Escape Velocity• The speed necessary to put a payload
infinitely far from Earth.
• 11.2 km/s horizontally or about 25,000 mph
vesc 2GM
r11.2km/s on Earth
Bonus• List all the planets in our solar system from
lowest escape velocity to highest and explain how you did it.