Define force of gravity.

The force of gravity is defined as the attractive force between two masses. This fundamental interaction pulls objects toward each other, and its strength depends on the masses involved and the distance between them, as described by Newton's law of universal gravitation. The gravitational force is what keeps planets in orbit around stars, moons around planets, and is responsible for the weight of objects on Earth.

Understanding the nature of gravitational force is critical in physical science, as it plays a crucial role in the motion of celestial bodies and the behavior of objects under the influence of gravity on Earth. The other concepts presented do not describe gravitational force; they pertain to other types of forces, such as friction or electromagnetic forces, which are distinct interactions within the framework of physics.