* Terminal velocity requires air resistance: Terminal velocity is the maximum speed an object reaches when falling through a fluid (like air). It occurs when the force of gravity pulling the object down is balanced by the force of air resistance pushing it up.
* No air resistance in a vacuum: In a vacuum, there is no air. Without air, there is no air resistance.
* Constant acceleration in a vacuum: In a vacuum, the only force acting on the penny is gravity. This means the penny will continue to accelerate at a constant rate (due to Earth's gravitational pull) and never reach a terminal velocity.
In short: A penny falling in a vacuum would just keep accelerating faster and faster.
