Transcript Newton`s Thought Experiment

Newton’s Thought Experiment
• If you throw an object 5 miles/sec. the object
will curve downward but if that curve matches
the curvature of the earth the object never
hits the earth.
• The object stays at a constant height above
the earth. The object is in orbit.
Gravity acts on the moon
as well as an apple
/www.physics.uc.edu
Satellites
• The farther from the earth, the less
gravitational force there is. The velocity to
stay in orbit decreases as objects move away
from the earth.
• LEO (low earth orbits) satellites are only 100
miles from the surface.
• LEO satellites must travel fast at 5 miles/sec.
• LEO satellites orbit the earth in 90 minutes.
LEO satellites
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Travel 100 miles from the surface
Move 300 miles per minute
Radio data to the ground
Often seen after dusk in the night sky
Geostationary Earth Orbit
• GEO satellites are 22,000 miles from earth
where gravitational force is weaker.
• GEO satellites can travel slower at 2 miles/sec.
• At 2 miles/sec and at a distance of 22,000
from earth it takes one day to orbit the earth.
• GEO satellites move with the earth, so they
are stationary relative to the earth.
GEO satellites
• Weather satellites
• Satellite TV
Receiving antennas
do not have to move
to stay in contact
with GEO satellites.
Medium Earth Orbit Satellites
• There are 24 GPS satellites that are about
12,000 miles from the earth
• Travel 7000 miles/hr, circling the earth twice in
less than a day.
• The GPS receiver receives signals from three
or more GPS satellites.
• The time for the signal to be received enables
the receiver to calculate distance from the
satellite.
Triangulation to determine location
http://www.gpssystems.org.uk/how-gps-works/
Resources
• Garmin Website
• Physics for Future Presidents, Richard Muller,
of UC Berkeley