Final answer:
The penny goes into the cup because of inertia; it remains in a state of rest and falls due to gravity when the card is flicked away. This demonstration exemplifies Newton's first law of motion.
Step-by-step explanation:
The reason the penny goes into the cup when the card is flicked is due to inertia. The penny will remain in a state of rest due to its inertia and when the card, which does not create a significant frictional force on the penny, is quickly removed or flicked out from underneath it, the penny is free to fall straight down due to gravity into the cup placed below it. This demonstrates Newton's first law of motion, where an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This inertia is the same principle that allows a tablecloth to be yanked out from under dishes, as seen in classic magic tricks or physics demonstrations.
Regarding the other scenarios provided for context in your question, such as the behavior of charged objects, and Newton's third law examples like action-reaction pair in Earth-Moon system, they illustrate various principles of physics such as electrostatics and motion. These examples highlight the diverse application of physical laws to explain different phenomena.