When an object enters a gravitational field, several things can happen depending on the properties of the object and the strength of the gravitational field. Here are the typical scenarios:
Freefall: If there are no other forces acting on the object apart from gravity, it will undergo freefall. This means the object will accelerate toward the source of the gravitational field (e.g., a planet or a star). The object will experience an increase in its velocity as it falls deeper into the gravitational field.
Orbit: If the object has sufficient initial velocity and is at the right distance from the gravitational source, it can enter a stable orbit. In this case, the gravitational force provides the centripetal force needed to keep the object in a curved path around the gravitational source. The object continuously falls toward the source but never collides with it.
Impact or collision: If the object does not have enough velocity to enter a stable orbit, it may collide with the gravitational source. This can happen when an object falls directly toward a planet or star and does not have enough horizontal velocity to establish an orbit. The outcome of the impact will depend on the mass and composition of the object as well as the nature of the gravitational source.
Trajectory alteration: In the presence of a gravitational field, objects traveling through space may have their trajectories altered. The gravitational field can cause the object's path to curve or bend, leading to changes in speed and direction. This effect is often utilized in gravitational assists or slingshot maneuvers, where spacecraft use the gravity of a planet or another celestial body to gain speed or alter their trajectory.
It's important to note that the behavior of an object in a gravitational field is described by Newton's laws of motion or, more accurately, by Einstein's theory of general relativity for strong gravitational fields or high speeds. The specifics of what happens to an object depend on various factors, including the object's mass, velocity, the mass of the gravitational source, and the distance between them.