When a satellite moves in a circular orbit around a planet, does it have constant momentum, velocity or acceleration?
When a satellite moves in a circular orbit around a planet, its velocity and momentum are constantly changing, but its acceleration remains constant. Here's why:
1. Velocity: Velocity is a vector quantity that describes the speed and direction of motion. In a circular orbit, the satellite's velocity is constantly changing because its direction is constantly changing. As the satellite moves around the planet, it is constantly being pulled towards the planet by gravity, which causes it to change direction. The satellite's velocity is highest at the point where it is closest to the planet (perigee) and lowest at the point where it is farthest from the planet (apogee). Therefore, the satellite's velocity is not constant but continuously changes throughout its orbit.
2. Momentum: Momentum is a vector quantity that depends on an object's mass and velocity. Since the satellite's velocity is constantly changing in a circular orbit, its momentum is also constantly changing. As the satellite moves closer to the planet, it speeds up, which increases its momentum. As it moves away from the planet, it slows down, leading to a decrease in momentum. However, the total momentum of the system (satellite+planet) remains constant because of the action-reaction principle. The changes in momentum of the satellite are always exactly balanced by corresponding changes in the momentum of the planet.
3. Acceleration: Acceleration is the rate of change of velocity. In a circular orbit, the satellite's acceleration is constant in magnitude but continuously changing in direction. The acceleration is always directed toward the center of the orbit, which is the planet. The centripetal acceleration keeps the satellite moving in a circle. This acceleration is provided by the gravitational force between the satellite and the planet. Since the acceleration is directed inward and perpendicular to the velocity vector, it does not change the speed of the satellite but changes only the direction of its motion.
In summary, when a satellite moves in a circular orbit around a planet, its velocity and momentum are continuously changing, but its acceleration remains constant.