How does the Satellite manage to stay in earth's orbit?

yalgaar · Apr 27, 2009

I have read that an object needs to have a velocity of around 8km/s to not fall back on earth and to stay on orbit.

Based on the above, are all our human made sattelites constantly travelling at around 8km/s to not fall back on earth? Is so doen't it need a lot of fuel? Does it store all this fuel? I think I am missing something basic here.

mgb_phys · Apr 27, 2009

It doesn't take any fuel to keep moving - there is nothing to stop it.

pixel01 · Apr 28, 2009

At 8km/s, if you fly through the atmosphere, probably your craft will burn

DaveC426913 · Apr 28, 2009

yalgaar said: ↑

I have read that an object needs to have a velocity of around 8km/s to not fall back on earth and to stay on orbit.

Based on the above, are all our human made sattelites constantly travelling at around 8km/s to not fall back on earth? Is so doen't it need a lot of fuel? Does it store all this fuel? I think I am missing something basic here.

Newton's First Law: an object in motion will tend to stay in motion. There is no air - and therefore no air resistance - in space. Once you get the craft up to speed, it will continue on its merry way forever until it encounters something to stop or slow it (such as faint whiffs of atmosphere in low orbit.)

DaveC426913 · Apr 28, 2009

pixel01 said: ↑

At 8km/s, if you fly through the atmosphere, probably your craft will burn

This is not relevant.

Nabeshin · Apr 28, 2009

http://en.wikipedia.org/wiki/Newton's_cannonball

Besides the appeal to inertia that DaveC and mgb have given, the newton's cannon example is a good illustration of orbits and why the orbiting object doesn't just "fall back to earth".