Transcript Rockets and Satellites

ROCKETS AND SATELLITES
Key Concepts
•How does a rocket lift off the
ground?
•What keeps a satellite in
orbit?
Key Terms
•Satellite
•Centripetal force
HOW DO ROCKETS LIFT OFF?
Rockets lift off because of
Newton’s third Law
 They burn fuel and push exhaust
gases downward at a high
velocity
 The gases push upward on the
rocket with an equal but opposite
force
 This upward pushing force is
called thrust
 Thrust must be greater than
gravity for the rocket to rise and
accelerate into space
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WHAT IS A SATELLITE?
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Any object that orbits another
object in space
Our moon is a natural satellite
Artificial satellites are
launched into orbit
Used for communications,
military intelligence, weather
analysis and geographical
surveys
The ISS (International Space
Station) is an example of an
artificial satellite
CIRCULAR MOTION
Artificial satellites travel around
Earth in almost circular path
 An object moving in a circular path is
accelerating because it is constantly
changing direction
 If an object is accelerating, a force
must be acting on it – called
centripetal force
 Centripetal means center seeking
 The Earth’s gravity is the centripetal
force for the satellite. It keeps pulling
the satellite towards the Earth
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SATELLITE MOTION
Q: Why don’t satellites fall to Earth like a thrown
ball does?
A: They have a greater horizontal velocity than a
ball thrown on Earth
EXPLANATION:
A ball thrown has horizontal force moving it
forward. Gravity is a force acting to pull it to the
ground. The more force you give the ball the
faster it travels horizontally and the greater
distance it travels before hitting the Earth
 A satellite in orbit around the Earth is
continuously falling towards the Earth, but
because the Earth is curved and they are
traveling so fast , they don’t hit but travel around
it
 A satellite is a falling projectile that keeps
missing the ground!!
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SATELLITE MOTION
A satellite does not need
fuel because it continues
to move ahead due to its
inertia
 Gravity continuously
changes its direction
 The speed required to
keep a satellite in orbit is
7,900m/s
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SATELLITE LOCATION
Mapping and observation satellites are put into
low orbits of less than 1,000 km
 Completes an orbit in less than 2 hours
 Satellites such as communications satellites put
into higher orbits (36,000 km) where they circle
the Earth in 24 hours Because of this they
remain over the same point on Earth –
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Geosynchronous orbit
SOURCES
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http://library.thinkquest.org/C0110484/content.php?id
=62
http://www.splung.com/content/sid/2/page/satellites
http://commons.wikimedia.org/wiki/File:Centripetal_f
orce.PNG
http://www.stockcarscience.com/scienceTopics/scsRaci
ng_CentrifugalForce.php
http://www.spacetoday.org/Satellites/YugoWarSats.ht
ml
http://www.nasa.gov/mission_pages/station/multimedi
a/sts114_7200.html
http://exploration.grc.nasa.gov/education/rocket/rktth
1.html