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CONCEPTUAL PHYSICS

CONCEPTUAL PHYSICS. Satellite Motion. Earth Satellites An earth satellite is a projectile that falls around Earth rather than into it. It has to have a tangential velocity fast enough to make its curved path match the curvature of the Earth.

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CONCEPTUAL PHYSICS

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  1. CONCEPTUAL PHYSICS Satellite Motion

  2. Earth Satellites • An earth satellite is a projectile that falls around Earth rather than into it. • It has to have a tangential velocity fast enough to make its curved path match the curvature of the Earth. • Earth’s curvature drops a vertical distance of 4.9m every 8000m. • If you throw a projectile at a horizontal velocity of 8km/s(29000 km/h), then it would follow the curvature of the Earth. • Orbital speed for close orbit to Earth is 8km/s. But, at this atmospheric friction would burn it. Thus, satellite must stay at about 150km above Earth’s surface.

  3. Circular Orbits • In circular orbit, the speed of a satellite is not changed by gravity. • For a satellite close to Earth, the time for a complete orbit about Earth, called the period, is about 90 minutes. For higher altitudes it is longer. • Elliptical Orbits • If a projectile is given a horizontal speed greater than 8km/s, it will overshoot a circular path and trace an oval shaped path called an ellipse. • \\Discovery\E\discovery videos\9th-12th Science\Planetary_Orbits_are_Elliptical.asf

  4. A satellite’s speed varies in an elliptical orbit. As it moves away from Earth it looses speed until it reaches a point where it no longer recedes and falls back to Earth and it regains its initial speed. (fig 12.9 p167) • Energy conservation and satellite motion • In circular orbit, the Kinetic Energy and Potential Energy is always constant, thus the speed is constant. • In an elliptical orbit, speed and distance vary. • Potential energy is greatest the farthest away (the apogee) and least when the satellite is the closest (the perigee) • At every point, the sum of potential energy and kinetic energy is the same. • Satellites - Elliptical Orbits

  5. Escape speed • “ What goes up must come down” • What vertical speed is sufficient enough to insure that what goes up will escape and not come down? • The answer is a speed greater than 11.2km/s. • Read Escape speed p 170 • v=  (2GM/d) • \\Discovery\E\discovery videos\9th-12th Science\Through_the_Ages__Measuring_the_Solar_System_and_Universe.asf • \\Discovery\E\discovery videos\9th-12th Science\Satellites_and_Telescopes__How_Scientists_Study_the_Sun.asf • \\Discovery\E\discovery videos\9th-12th Science\The_Planets_of_Our_Solar_System.asf

  6. What is the escape speed for the moon if its mass=7.35x1022 kg and its radius (d)= 1.74x106 m? • How fast would the moon need to travel to escape the gravitational pull of the Earth, if Earth has a mass of 5.98x1024 kg and the distance from the Earth and the moon is 3.84x108 m?

  7. CONCEPTUAL PHYSICS Satellite Motion

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