Why does a satellite in orbit have constant velocity?

A satellite in orbit has constant velocity due to the balance between gravitational pull and its forward momentum.

In more detail, a satellite in orbit around the Earth is in a state of free fall. It is constantly falling towards the Earth due to the force of gravity, but it also has enough forward momentum to keep missing the Earth. This is what creates an orbit. The satellite is essentially falling around the Earth, and this is why it maintains a constant velocity.

The velocity of a satellite in orbit is determined by two factors: its altitude and the mass of the planet it's orbiting. The higher the altitude, the slower the required orbital speed. Conversely, the greater the mass of the planet, the faster the required orbital speed. This is due to the inverse square law of gravity, which states that the force of gravity decreases with the square of the distance from the source.

The velocity of the satellite remains constant because the forces acting on it are balanced. The gravitational pull of the Earth is constantly pulling the satellite towards it, while the satellite's forward momentum is constantly trying to carry it in a straight line. These two forces balance each other out, resulting in a curved path that we call an orbit.

In a perfect vacuum, with no other forces acting on the satellite, it would maintain this constant velocity indefinitely. However, in reality, there are other forces at play, such as atmospheric drag and solar radiation pressure, which can cause the satellite's orbit to decay over time. But for the most part, and certainly for the purposes of your physics studies, you can consider the velocity of a satellite in orbit to be constant.

Remember, this is a simplification of a complex physical phenomenon. In reality, orbits can be elliptical, not perfectly circular, and other factors such as the gravitational pull of other celestial bodies can also come into play. But the basic principle remains the same: a satellite in orbit maintains a constant velocity due to the balance between gravitational pull and its forward momentum.