A satellite is in a circular orbit around Earth at an altitude at which air resistance is negligile. Which one of the following statements is true? A. There is only one force acting on the satellite. B. There are two forces acting on the satellite and their resultant is 0. C. There are two forces acting on the satellite and their resultant is NOT 0. D. There are three forces acting on the satellite. E. None of the preceding statements are correct. I'm teetering between A and B. My problem is just that I seem to be able to justify anything to myself and it confuses me. Here's what's going through my mind: Force 1: Gravity. The earth pulls on the satellite. Possible Force 2: Centripetal Force. Why yes: If there were no force to counteract gravity, the satellite would succumb to gravity and accelerate toward the center of earth. Therefore, a second force is necessary. Why no: (Maybe this is just a lame excuse for logic that's just stuck in my mind.) While the earth currently pulls the satellite (gravity), it's actually a force which previously propelled the satellite to such a velocity to reach a free fall state that keeps the satellite in orbit. The satellite tends to stay on its instantaneous trajectory, because as inertia explains, it just does. In each instant, the earth pulls it onto a slightly different trajectory. Possible Force 3: Gravity. The sun pulls on the satellite. Possible Force 4: Centripetal Force. Orbit around the sun. Infinitely More Forces: Gravity (each planet in the universe). Centripetal Force (motion of galaxy through universe). I realize that I'm probably just making this more complicated than it needs to be, but it seems that I never understand what my teacher is trying to ask. If I decide to zero in on just the satellite and earth, he includes the sun. If I include the sun, he's only looking at the satellite and earth. Not so fun on my multiple choice assignments.