Why are satellites placed into orbit at least 150 km above earth’s surface?

to avoid air resistance
to match earth’s curvature
to create inertia
to increase friction

The correct answer is to avoid air resistance

Satellites are moving in the orbit because of the initial force that was applied through the rockets. Now for the satellites to remain in orbit there should not be any friction. As air resistance is also friction that is provided by air, the satellites are 150KM above the surface to avoid air resistance  

some think that theories become laws, but theories and laws have separate and distinct roles in the scientific method. a law is a description of an observed phenomenon in the natural world that hold true every time it is tested. it doesn't explain why something is true; it just states that it is true.

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a charge 3q is at the origin, and a charge −2q is on the positive x axis at x=a. part a where on the x-axis would you place a third charge so it would experience no net electric force? enter an expression for the exact answer, which will involve a square-root sign. (do not enter an approximate decimal answer.)