Artificial satellites orbit the earth because of free falling. Then when we jump off a plane why we directly hit the ground?
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When you jump off... anything, you are in free fall AND in orbit around Earth's centre. Unfortunately, two things happen:
1. The ground gets in your way (and you crash) before you complete your orbit.
2. Air resistance slows you down so that very rapidly, in your fall, you are no longer in free fall (you will have reached "terminal velocity" and the air resistance will be equal to your weight)
Satellites are above the atmosphere where number 2 does not act on them, and they are moving so fast sideways that the ground never gets in their way.
If you could find a plane that can move sideways at 8 km/s (over 17000 mph) AND if air resistance could be eliminated, then you would fall down at the same rate as the ground curves away from you. You would remain at the same "altitude".
But that situation is impossible... unless you are in space on a satellite.
When astronauts go outside (from the space station for example), they are "falling" sideways at the same speed as the space station and there is no air resistance. Therefore, the astronaut remains on the same orbit as the station. From his point of view, he is stationary relative to the space station.
But we know that they are both moving sideways at over 17,000 mph.
1. The ground gets in your way (and you crash) before you complete your orbit.
2. Air resistance slows you down so that very rapidly, in your fall, you are no longer in free fall (you will have reached "terminal velocity" and the air resistance will be equal to your weight)
Satellites are above the atmosphere where number 2 does not act on them, and they are moving so fast sideways that the ground never gets in their way.
If you could find a plane that can move sideways at 8 km/s (over 17000 mph) AND if air resistance could be eliminated, then you would fall down at the same rate as the ground curves away from you. You would remain at the same "altitude".
But that situation is impossible... unless you are in space on a satellite.
When astronauts go outside (from the space station for example), they are "falling" sideways at the same speed as the space station and there is no air resistance. Therefore, the astronaut remains on the same orbit as the station. From his point of view, he is stationary relative to the space station.
But we know that they are both moving sideways at over 17,000 mph.
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A satellite is falling toward the Earth all the time, but it continually misses hitting Earth because of its lateral speed. This is not an analogy but one of several correct ways to view an orbit.
A person jumping from a plane (except for wind resistance) is free falling. If the plane you were jumping from were traveling very fast, you would travel farther in the direction of its flight before hitting the ground. It the plane were traveling much faster still, because of the curvature of the Earth you may not hit the ground until you were on the other side of it. If the plane were moving even faster, you may not hit the ground at all, but continually miss. You would be in orbit.
A person jumping from a plane (except for wind resistance) is free falling. If the plane you were jumping from were traveling very fast, you would travel farther in the direction of its flight before hitting the ground. It the plane were traveling much faster still, because of the curvature of the Earth you may not hit the ground until you were on the other side of it. If the plane were moving even faster, you may not hit the ground at all, but continually miss. You would be in orbit.
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