When a bullet is shot into the air, its trajectory is initially determined by the force and angle with which it was fired. As it travels upward, the bullet is subject to the force of gravity, which eventually slows it down and causes it to reverse direction, falling back toward the ground.
The exact behavior of a bullet shot into the air depends on various factors, such as its initial velocity, mass, shape, and atmospheric conditions. In most cases, the bullet will follow a parabolic trajectory. As it ascends, its velocity decreases due to the opposing force of gravity until it reaches its highest point, known as the apex. At the apex, the bullet's velocity momentarily becomes zero before it begins its descent.
When the bullet starts to fall back down, it gains speed due to the gravitational force pulling it downward. As it nears the ground, the bullet's speed increases, and it eventually reaches its terminal velocity, which is the maximum speed it can attain due to the resistance from air friction. The terminal velocity depends on the bullet's mass, shape, and the density of the air.
It's important to note that firing a bullet into the air is extremely dangerous and highly discouraged. The bullet can reach high altitudes and, as it falls back down, it can retain enough velocity to cause injury, damage property, or even be fatal upon impact. Shooting firearms should always be done responsibly and with regard for the safety of oneself and others.