# How do satellites move around the earth

## Understand physics 4, textbook

33 Curved paths on earth and in space  Learning objective control 8, page 87 4. What causes the orbit of a satellite? If a body is shot from a mountain in a horizontal direction, it falls to the ground in a parabolic curve due to the force of gravity. From a certain high speed the body no longer hits the ground, but “falls” around the earth. It is then on a satellite orbit. Every second he wants to move in a straight line at high speed due to his inertia. The attraction constantly distracts him, so that the distance to the earth is always the same. M The satellite orbit is created by the interaction of the straight and uniform inertial motion (in the direction of the circular orbit tangent) and the uniformly accelerated falling motion in the direction of the earth. 5. What do we mean by circulation and escape speed? At an orbit speed of approx. 7.9 km / s, a satellite always remains at the same distance from the earth. If the speed is increased, an elliptical orbit is created after the engines are switched off. The ellipse becomes more and more elongated, the greater the speed. At 11.2 km / s or more, the earth's gravity is no longer sufficient to “bring back” the body. It is now moving away from the earth in an increasingly flatter curve. This so-called escape speed is needed to be able to send space probes on their way to the other planets. M In order for a satellite to remain in a near-earth orbit, it must have a speed of 7.9 km / s (= 28,000 km / h). The escape speed is 11.2 km / s (= approx. 40,000 km / h) so that he can leave earth orbit. 6. Why do bodies appear weightless in a circling spaceship? The still existing weight is counteracted by an equally large centrifugal force. The circular motion of the satellite is considered to be "falling". No weight can be determined during the fall. Inertial and falling motion Trajectory with increasing launch speed composite satellite motion from: 33.1 Consideration of the creation of a near-earth satellite orbit 33.2 Rocket launch: A satellite is brought into orbit. 33.4 International Space Station (ISS) 33.5 A telecommunications satellite in its orbit 33.6 Astronaut training on weightlessness Centrifugal force Weight force Earth 33.3 Causes of weightlessness on a circular orbit For testing purposes only - property of the publisher öbv