The Earth curves approximately 5 meters downward for every 8000 meters along its horizon. If you were to look out horizontally along the horizon of the Earth for 8000 meters, you would observe that the Earth curves downwards below this straight-line path a distance of 5 meters. In order for a satellite to successfully orbit the Earth, it must travel a horizontal distance of 8000 meters before falling a vertical distance of 5 meters. A horizontally launched projectile falls a vertical distance of 5 meters in its first second of motion. To avoid hitting the Earth, an orbiting projectile must be launched with a horizontal speed of 8000 m/s. When launched at this speed, the projectile will fall towards the Earth with a trajectory which matches the curvature of the Earth. As such, the projectile will fall around the Earth, always accelerating towards it under the influence of gravity, yet never colliding into it since the Earth is constantly curving at the same rate. Such a projectile is an orbiting satellite
2.5 rockets and satellites
Chapter 2: Forces Miss Luzma Fabre
Section 5: Rockets and satellites• Sputnik I was the first Earth-orbiting artificial satellite (1957). It was launched by the Soviet Union• Then, in 1958, USA launched a satellite called Explorer I.
How do rockets lift off?• Rockets and space shuttles lift into space using Newton ´s third law of motion• A rocket can rise into the air because the gases it expels with a downward action force exert an equal but opposite reaction force on the rocket
• If the upward pushing force (thrust) is greater than the downward pull of gravity, the rocket will accelerate upward
The Saturn V (five) rocket wasdeveloped in 1960’s. How do thesemultistage rockets work? • Once a stage uses up its fuel, the container drops off and the next stage ignites
What is a satellite?• Rockets are used to carry satellites into space• A satellite is any object that orbits another object in space• Artificial satellites are designed for different purposes:• Communication• Military intelligence• Weather analysis• Geographical surveys
• Circular motion• Satellites travel around Earth in circular paths• They are constantly changing direction= accelerating, so a force must be acting on them• CENTRIPETAL FORCE
• Any force that causes an object to move in a circular path is a centripetal force• The gravitational force is the centripetal force that pulls the satelite toward the center of the Earth
• Does a satellite require fuel once it is in orbit? Why?• No, because it continues to move ahead due to its inertia. At the same time, gravity continuously changes the satellite´s direction
• Satellites in orbit around Earth continuously fall toward Earth, but because Earth is curved they travel around it.• Is like a falling projectile that keeps missing the ground
• The faster a projectile is thrown, the farther it travels before it hits the ground. A projectile with enough velocity (7900 m/s) moves in a circular orbit
Launch Speed equal to 8000 m/s Projectile orbits Earth - Circular PathLaunch Speed less than 8000 m/sProjectile falls to Earth
• Satellite location• They orbit at different heights, depending on their uses• Ex: communications satellites travel about 36000 km above Earth´s surface
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