Horizontal
velocity does not prevent an object from falling or keep it in the air any
longer
However,
since the earth is not flat, a very large horizontal velocity would allow an
object to travel so far horizontally that it would fall over the horizon, and
stay in the air longer.
With
enough horizontal velocity, an object would keep missing the earth and fall
forever, never hitting the ground unless something took away its horizontal
velocity. This is how objects are put
into orbit.
Air
friction takes horizontal velocity away from objects, so if you want something to orbit, you need
to get out of the atmosphere.
Satellites
are sent into space because there is no air friction there to rob them of their
horizontal velocity, not because gravity is weaker.
If
you took away the moon’s horizontal velocity, it would fall straight to
earth. But since there is no friction in
space, it will not loose its horizontal velocity, and it will orbit forever.
Spaceships
in orbit do not have to fire their engines to remain in orbit,
they simply fall – around the earth.
The
closer a satellite is to earth, the faster it will orbit.
John
Glenn was the first American to orbit the earth. It took his ship 88 minutes to complete one
orbit. He orbited at an altitude between
100 and 160
miles up, at a velocity of 17,000 mi/hr.
By
contrast, the moon orbits at an altitude of 240,000 miles at a velocity of 2,300 mi/hr and
takes 27.3 days to complete one orbit.
Geosynchronous
orbit occurs when a satellite takes exactly one day to orbit the earth. This can only occur if the satellite is at an
altitude of 35,786 km (22,241 miles) and
traveling at a velocity of 7,000 mi/hr.