Gravitational Force in Circular Orbit

Steps:

• Satellite moves in uniform circular motion with constant speed, requiring centripetal acceleration toward the orbit's center.
• Centripetal force is provided by the planet's gravitational attraction, the only horizontal force acting on the satellite.
• Gravitational force acts radially inward, directly toward the planet's center.
• At the shown position, this force direction matches the radial inward vector.

Why D is correct:

• D aligns with Newton's law of universal gravitation, where force is attractive and directed toward the planet's center, supplying the necessary centripetal force.

Why the others are wrong:

• A points radially outward, opposing the required centripetal direction.
• B points tangential forward, which would increase speed but not curve the path.
• C points tangential backward, which would decrease speed but not provide centripetal force.

Final answer: D