This question compares centripetal acceleration at different orbital radii. In circular orbit, gravitational force provides the centripetal force required for circular motion. The centripetal acceleration equals v²/r, but for orbits, the relationship is more directly given by GM/r², where acceleration decreases with the square of the distance. Since the satellite at radius r is closer to the planet, it experiences stronger gravitational field and thus larger inward acceleration. Choice A incorrectly focuses on path length rather than gravitational field strength. When comparing orbital accelerations, remember that closer orbits require greater centripetal acceleration due to stronger gravitational fields.

This question identifies the direction of gravitational acceleration in orbital motion. In circular orbit, gravitational force provides the centripetal force required for circular motion. Gravitational acceleration always points toward the center of the gravitating body, regardless of the spacecraft's position or velocity direction. At point H1, even though the velocity is tangent east, the gravitational acceleration points radially inward toward the planet's center. Choice A incorrectly suggests the acceleration follows the velocity direction. When finding gravitational acceleration direction, remember it always points toward the center of the attracting mass.

This question relates orbital speed to orbital radius. In circular orbit, gravitational force provides the centripetal force required for circular motion. For circular orbits around the same planet, the relationship v = √(GM/r) shows that higher orbital speed corresponds to smaller orbital radius. The faster satellite must be at the smaller radius to maintain the balance between gravitational force and centripetal force requirements. Choice B incorrectly suggests the slower satellite is closer. When relating orbital speed to radius, use the inverse relationship: higher speed corresponds to smaller radius for circular orbits.

This question examines the gravitational force in orbital motion. In circular orbit, gravitational force provides the centripetal force required for circular motion. The gravitational force on the satellite always points toward Earth's center, regardless of the satellite's position in the orbit. This inward gravitational force acts as the centripetal force that keeps the satellite in circular motion. Choice D incorrectly suggests the force points outward, which would cause the satellite to spiral away from Earth. To identify gravitational force direction, remember that it always points toward the center of the gravitating body.

This question explains the cause of curved motion in orbital dynamics. In circular orbit, gravitational force provides the centripetal force required for circular motion. The velocity direction changes because a net inward force (gravitational force) produces centripetal acceleration toward the center. This acceleration continuously turns the velocity vector, causing the satellite to follow a curved path rather than moving straight. Choice A incorrectly suggests tangential force speeds up the satellite, but tangential force would change speed, not direction. To explain curved motion, identify that perpendicular net force causes acceleration that changes velocity direction.

This question addresses orbital mechanics and energy changes. In circular orbit, gravitational force provides the centripetal force required for circular motion. To move to a larger radius orbit, the spacecraft needs more energy. Briefly increasing speed in the tangential direction adds kinetic energy, which transforms the circular orbit into an elliptical transfer orbit that reaches a higher altitude. Choice B incorrectly suggests radial thrust, which would change the orbit shape rather than the energy. When changing orbital radius, apply tangential thrust to change orbital energy rather than radial thrust.

This question tests understanding of the motion of orbiting satellites. The gravitational force follows Newton's law: F = GMm/r², which decreases with the square of the distance. At radius r, the force is GMm/r², while at radius 2r, it becomes GMm/(2r)² = GMm/4r², which is one-fourth as strong. This means gravity is stronger on satellites closer to the planet, providing the greater centripetal force needed for their faster orbital motion. Choice B incorrectly treats gravity as a constant mg, which only applies near Earth's surface, not for orbital distances. The strategy is to remember that gravitational force follows an inverse square law: doubling distance reduces force to one-fourth.

This question tests understanding of the motion of orbiting satellites. From the orbital equation GMm/r² = mv²/r, we can solve for speed: v = √(GM/r). Notice that the satellite's mass m cancels out, meaning orbital speed depends only on the planet's mass M and orbital radius r. This is because while a more massive satellite experiences stronger gravity (F ∝ m), it also requires more force to accelerate (F = ma), and these effects exactly cancel. Choice A incorrectly assumes mass affects speed, ignoring this cancellation. The strategy is to remember that orbital speed is independent of satellite mass—all objects orbit at the same speed at a given radius.

This question tests understanding of the motion of orbiting satellites. The centripetal force required for circular motion is Fc = mv²/r, which increases with the square of the speed. If a satellite's speed increases while maintaining the same radius, the required centripetal force must increase proportionally to v². Since gravity at a fixed radius r remains constant (GMm/r²), the satellite would need additional inward force to maintain circular motion at the higher speed. Choice B incorrectly suggests that faster motion requires less force, contradicting the physics of circular motion. The strategy is to remember that centripetal force depends on v²—doubling speed quadruples the required force.

This question tests understanding of the motion of orbiting satellites. For any object in circular motion, a centripetal force directed toward the center is required to continuously change the velocity's direction. In the case of a satellite orbiting a planet, the gravitational force provides this centripetal force, pulling the satellite toward the planet's center. This inward force causes the satellite to continuously accelerate toward the center, changing its velocity direction to maintain circular motion. Choice A is incorrect because centrifugal force is a fictitious force that only appears in rotating reference frames, not an actual force acting on the satellite. The key strategy is to remember that for orbital motion, gravity IS the centripetal force—no additional forces are needed.