You might've heard of the term terminal Velocity before, it refers to the maximum velocity that an object can achieve as it falls through a fluid (most of the time air ).
This happens when its speed is constant due to the restraining force exerted by the fluid through which it is moving, the downwards force of gravity will be compensated by the upwards drag force and buoyancy (which we've neglected in the above formula) .
As a falling object accelerates, its drag force grows, here the drag force is proportional to the square of its velocity by a factor K which depends on the fluid and the shape of the object.
This formula is obtained through Newton's second law, we consider 2 forces, gravity and drag. And there is no acceleration at terminal velocity.
For your information a skydiver typically falls at 200 km/h in a free-fall position with a half open parachute.
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