What it is:

* Terminal velocity is the maximum speed an object can reach while falling through a fluid (like air or water). It occurs when the force of gravity pulling the object down is balanced by the force of drag (air resistance) pushing it up.

* It's not a constant speed. Terminal velocity varies depending on several factors:

* Object's shape: A streamlined object (like a skydiver) will have a lower terminal velocity than a less aerodynamic object (like a rock).

* Object's mass: A heavier object will experience a stronger gravitational force and therefore have a higher terminal velocity.

* Fluid density: The denser the fluid, the greater the drag force and the lower the terminal velocity. This is why you fall slower in water than in air.

* Object's surface area: The larger the surface area, the greater the drag force, and the lower the terminal velocity.

Key Properties:

* Constant velocity: Once terminal velocity is reached, the object's speed remains constant.

* Dynamic equilibrium: The forces acting on the object are balanced (gravity downwards, drag upwards).

* No acceleration: Since the speed is constant, the object is no longer accelerating.

* Dependent on factors: Terminal velocity is not a fixed value for an object. It depends on the factors mentioned above, so it can vary significantly.

Examples:

* Skydiving: Skydivers reach terminal velocity around 120 mph (193 km/h) in a belly-to-earth position. Opening a parachute drastically increases their surface area, reducing their terminal velocity and allowing them to land safely.

* Raindrops: The size and shape of raindrops determine their terminal velocity. Larger raindrops fall faster than smaller ones.

Important Note: It's crucial to remember that terminal velocity is a concept related to falling objects. It doesn't apply to objects moving horizontally or objects with a propulsion system (like a car or airplane).