When an artificial satellite revolves around the Earth in a circular orbit, which of the following quantities remains constant?

To determine which quantity remains constant for a satellite in a circular orbit, we must analyze the physics of uniform circular motion and central forces:A) Linear velocity: Incorrect. Velocity is a vector quantity, meaning it has both magnitude (speed) and direction. While the speed of the satellite is constant in a circular orbit, its direction is constantly changing as it curves around the Earth. Therefore, linear velocity is not constant.B) Angular frequency ($\omega$): Correct. In a stable circular orbit, the satellite covers equal angles in equal intervals of time. Since the orbital period ($T$) and the rate of rotation are steady, the angular frequency (or angular velocity magnitude) remains constant.C) Angular momentum ($L$): Correct. For a satellite, the gravitational pull of the Earth acts as a central force (it always points toward the center of the Earth). Since the force is central, there is no external torque ($\tau = 0$) acting on the system. According to the law of conservation of angular momentum, if the torque is zero, the angular momentum remains constant.D) Angular displacement ($\theta$): Incorrect. Angular displacement refers to the angle through which the satellite has moved. As the satellite continues to revolve, this angle increases over time.Why both B and C could be considered?In the context of standard competitive exams (like UPSC), Angular Momentum is the most "fundamental" physics answer because it remains constant due to the absence of external torque. However, in a perfect circular orbit, Angular Frequency is also constant. Usually, in these multiple-choice formats, C is the prioritized answer because it holds true even if the orbit were slightly elliptical (Kepler's Second Law), whereas angular frequency would vary in an ellipse.Conclusion:In a circular orbit, the satellite experiences a central force, ensuring its angular momentum is conserved.