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R OCKETS AND S ATELLITES Key Concepts How does a rocket lift off the ground? What keeps a satellite in orbit? Key Terms Satellite Centripetal force.

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Presentation on theme: "R OCKETS AND S ATELLITES Key Concepts How does a rocket lift off the ground? What keeps a satellite in orbit? Key Terms Satellite Centripetal force."— Presentation transcript:

1 R OCKETS AND S ATELLITES Key Concepts How does a rocket lift off the ground? What keeps a satellite in orbit? Key Terms Satellite Centripetal force

2 H OW 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

3 W HAT IS A SATELLITE ? 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

4 C IRCULAR M OTION 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

5 S ATELLITE M OTION 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

6 E XPLANATION : 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!!

7 S ATELLITE M OTION 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

8 S ATELLITE L OCATION 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 – Geosynchronous orbit

9 S OURCES 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


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