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Satellites Dynamics lesson 4. Any mass is able to attract another mass The attraction force is directly proportional to the product of the two masses.

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Presentation on theme: "Satellites Dynamics lesson 4. Any mass is able to attract another mass The attraction force is directly proportional to the product of the two masses."— Presentation transcript:

1 Satellites Dynamics lesson 4

2 Any mass is able to attract another mass The attraction force is directly proportional to the product of the two masses The attraction force is indirectly proportional to the distance between their centres squared A proportionality constant appears: The constant of universal gravitation G Law of universal gravitation F g = · M · m r2r2 Any mass is able to attract another mass The attraction force is directly proportional to the product of the two masses The attraction force is indirectly proportional to the distance between their centres squared A proportionality constant appears: The constant of universal gravitation G G

3 A 3rd law evidence M m M is attracting m with a force of: m is attracting M with a force of: FgFg FgFg F g = G · M · m m · M r2r2 r2r2 F g and F g are a pair of action-reaction forces!! same magnitudeopposite sensesame direction

4 Earth & Moon I FgFg - The Earth is attracting the Moon Why does the Moon not fall? Houston, we have a problem!! - There is no other force on the Moon - F g is an unbalanced force - It should induce a change in the Moon’s motion F g is actually changing Moon’s motion, but not its speed, it‘s changing the direction of its velocity.

5 Earth & Moon II FgFg v FgFg v FgFg v FgFg v The force of attraction of the Earth, changes one property of the Moon’s velocity: direction Why? A force perpendicular to a velocity, produces a change in the direction, not in the magnitude of the velocity

6 Tides · · · · rotational sense The Moon attracts large masses of water 24:00 h18:00 h12:00 h 6:00 h Low tide High tide A high tide here? Where does the attraction come from?

7 Artificial satellites - They are specially designed to follow an orbit. - Their period and frequency are accurately known. - Their applications are huge. Trajectory described around the Earth Period (T): time needed to complete a whole lap. I.S. units: s Frequency ( ): number of laps per second. I.S. units: s -1 telecommunications meteorology military research Hispasat Astra Meteosat NOAA NAVSTAR GPS Hubble MIR video

8 Satellite’s orbits Polar orbitGeostationary orbit video list of satellites video


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