Centripetal force in satellite orbits

Steps:

• Circular motion requires a centripetal force directed towards the center of the path.
• For a satellite, the gravitational force from Earth provides this centripetal force.
• Gravity acts radially inward, towards Earth's center.
• This inward force keeps the satellite in a stable circular orbit.

Why D is correct:

• Newton's law of universal gravitation states the force is attractive, directed towards the center of mass (Earth), matching the centripetal force requirement $F_c = \frac{mv^2}{r}$ towards the orbit's center.

Why the others are wrong:

• A: Repulsive force would push the satellite outward, causing it to escape orbit.
• B: Force in the direction of motion would accelerate it tangentially, not curve the path.
• C: Opposing motion would decelerate the satellite linearly, not provide circular turning.

Final answer: D