ASVAB (Armed Services Vocational Aptitude Battery)Mechanical Comprehension (MC)Medium
A satellite orbits Earth at a constant speed in a circular path. Which statement accurately describes the forces acting on the satellite?
- AA constant centrifugal force acts away from the center of Earth.
- BThere is no net force acting on the satellite.
- CThe force of gravity is balanced by the force of its forward motion.
- DA constant centripetal force acts towards the center of Earth.
Show answer & explanationAnswer & explanation
Correct answer: D. A constant centripetal force acts towards the center of Earth.
For an object to move in a circular path, a net force directed towards the center of the circle is required. This is called centripetal force. In the case of a satellite, gravity provides this centripetal force, continuously pulling the satellite towards Earth's center and preventing it from flying off into space.
Why the other options are wrong
- A. Incorrect. Centrifugal force is an apparent (fictitious) force experienced in a rotating reference frame, not an actual force acting on the satellite.
- B. Incorrect. A net force *is* acting on the satellite (centripetal force) to keep it in orbit; otherwise, it would move in a straight line (Newton's First Law).
- C. Incorrect. Gravity provides the centripetal force, and the satellite's forward motion is its velocity, not a force that balances gravity.
Centripetal Force
A net force that acts on an object moving in a circular path and is directed towards the center of the circle. It is essential for maintaining circular motion.
- Always perpendicular to the object's velocity.
- Examples: gravity on satellites, tension in a string swinging a ball.
- Formula: Fc = mv²/r.
Memory trick: Center-seeking force keeps circles neat.