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# Video:Explaining Newton's Law of Gravity

with Amrita Ngen

Sir Isaac Newton's Law of Gravity states there is a gravitational force between all objects in the universe. The law of gravity is a fundamental principle in physics.See Transcript

## Transcript:Explaining Newton's Law of Gravity

Newton's law of gravity defines the attractive force between all objects that possess mass. Understanding the law of gravity, one of the fundamental forces of physics, offers profound insights into the way our universe functions.

### Sir Isaac Newton’s Law of Gravity

The famous story that Newton came up with the idea for the law of gravity by having an apple fall on his head is not true, although he did begin thinking it when he saw an apple fall from a tree. He wondered if the same force at work on the apple was also at work on the moon. If so, why did the apple fall to the Earth and not the moon? Gravitational Forces

### Law of Gravity Is Universal

Newton eventually came to the conclusion that, in fact, the apple and the moon were influenced by the same force – that is gravity. He defined it as: Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles, and inversely proportional to the square of the distance between them.

### The Equation for Law of Gravity

Mathematically, this translates into the force equation. In this equation, the quantities are defined as: Fg = The force of gravity (typically in newtons) G = The gravitational constant, which adds the proper level of proportionality to the equation. m1 & m1 = The masses of the two particles (typically in kilograms) r = The straight-line distance between the two particles (typically in meters) This equation gives us the magnitude of the force, which is an attractive force and therefore always directed toward the other particle. As per Newton's Third Law of Motion, this force is always equal and opposite.