Terminal velocity is the constant speed that a freely falling object eventually reaches when the force of air resistance equals the force of gravity.

Here's how it works:

* Gravity: As an object falls, gravity pulls it downwards, causing it to accelerate.

* Air resistance: As the object falls faster, it encounters more air resistance, which acts as an opposing force.

* Terminal velocity: When the force of air resistance becomes equal to the force of gravity, the object stops accelerating and reaches a constant speed, which is the terminal velocity.

Factors affecting terminal velocity:

* Mass of the object: A heavier object has a higher terminal velocity.

* Shape and size of the object: Objects with larger surface areas experience more air resistance and therefore have lower terminal velocities.

* Density of the air: The denser the air, the higher the air resistance and the lower the terminal velocity.

Examples:

* A skydiver reaches a terminal velocity of about 120 miles per hour (190 km/h).

* A raindrop has a much lower terminal velocity due to its small size and shape.

* A feather has an even lower terminal velocity because of its light weight and large surface area.

Note: Terminal velocity is not a fixed value. It varies depending on the factors mentioned above.