Final answer:
The coin placed on the index card falls into the container below due to inertia, where the coin remains at rest due to insufficient frictional force to move it when the card is flicked. This exemplifies Newton's first law, demonstrating that without enough frictional force, the coin simply falls due to gravity.
Step-by-step explanation:
Understanding the Physics Behind a Coin Dropping into a Container
When the index card is flicked sideward causing the 25-cent coin to fall into the container below it, it is due to a concept in physics known as inertia, which is part of Newton's first law of motion. Inertia is the resistance of any physical object to any change in its velocity, which includes changes to the object's speed or direction of motion. Therefore, the correct answer to why the coin does not move with the direction of the force is a) Friction between the coin and index card.
When the card is flicked quickly, the force of friction between the coin and the card is not sufficient to overcome the coin's inertia. The frictional force needs to be greater than the force applied by the card to move the coin. Since the coin has inertia, it wants to remain in its state of rest relative to the card, and when the card is removed from underneath it, the coin simply falls due to gravity into the container.
This concept is similar to the classic tablecloth trick, where a swift pull of the cloth can leave plates and cutlery on the table due to inertia. The coin's inertia leads it to fall vertically downwards, not horizontally with the flick of the card, illustrating Newton's first law of motion in everyday life. In contrast to other forces like air resistance or magnetic force, friction and inertia are the main contributors in this scenario.