1. Universal Gravitation:
* Newton's Law of Universal Gravitation states that every particle in the universe attracts every other particle with a force that is:
* Proportional to the product of their masses: The more massive the objects, the stronger the gravitational attraction.
* Inversely proportional to the square of the distance between their centers: The farther apart the objects are, the weaker the gravitational force.
* The Earth's Mass: The Earth has a massive amount of mass, creating a strong gravitational pull on objects near its surface.
2. Direction of Gravitational Force:
* Center of Mass: The Earth's gravitational force always acts towards its center of mass. This center is located roughly at the Earth's geometric center.
* Vertical Direction: Since the Earth is roughly a sphere, the direction towards its center from any point on its surface is essentially vertically downwards.
3. Ignoring Air Resistance:
* Simplified Model: When discussing acceleration due to gravity, we often ignore air resistance. In reality, air resistance plays a role, but for many situations, it's negligible.
* Free Fall: In a vacuum (no air resistance), objects would fall vertically downwards under the influence of gravity alone.
Conclusion:
The combination of the Earth's massive mass, the direction of its gravitational force towards its center, and the simplification of ignoring air resistance leads to the observation that acceleration due to gravity always points vertically downward.
