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# Newton's Third Law Easy Q watch

1. What are two equal and opposite forces acting betwen and orbiting satellite and the Earth?

From CGP AS Revision Guide.
2. pull of earths gravity onto the satellite and the pull of satellites gravity onto the earth
3. Hi gaary has made a valiant attempt to answer your question; however, there is a discrepancy: if both the forces were due to gravity, both would be pulling the satellite towards the earth, so they would NOT be opposite., and satellite would crash onto earth!

The first point is correct i.e. the earth's gravity pulling satellite towards it; the force keeping the satellite from being pulled by the earth ]which would tend to make the satellite crash onto the earth (not good news!)] is the centrifugal force produced by the satellite orbiting the earth; this centrifugal force is tending to make the satellite disappear into outer space, but is balanced by the equal and opposite pull of the earth's gravitational force.

Hope this makes sense!

Mukesh (Science tutor)
4. (Original post by macpatelgh)
Hi gaary has made a valiant attempt to answer your question; however, there is a discrepancy: if both the forces were due to gravity, both would be pulling the satellite towards the earth, so they would NOT be opposite., and satellite would crash onto earth!

The first point is correct i.e. the earth's gravity pulling satellite towards it; the force keeping the satellite from being pulled by the earth ]which would tend to make the satellite crash onto the earth (not good news!)] is the centrifugal force produced by the satellite orbiting the earth; this centrifugal force is tending to make the satellite disappear into outer space, but is balanced by the equal and opposite pull of the earth's gravitational force.

Hope this makes sense!

Mukesh (Science tutor)
It does not make sense. It may be good that you review newton's laws again. Why satellite does not "disappear" into outer space is NOT because the centrifugal force is balanced by the equal and opposite pull of the earth's gravitational force.

To make it more explicit, sometimes, people would say the following:

The gravitational force that the Earth exerted on the Satellite is equal and opposite to the gravitational force that the Satellite exerted on the Earth .

Mathematically, it would be written as:
5. Just a reminder that will help you towards any question you may encounter about satellites, make sure you know the difference between centrifugal and centripetal force.

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