The Concept of Gravity

What is Gravity?

Gravity is a fundamental force of the universe that pulls objects towards each other. 

Gravity on Earth

• Gravity gives weight to physical objects and causes them to fall toward the Earth when dropped. 
• The acceleration due to gravity on Earth’s surface is approximately 9.8 m/s². 
• Any object will increase its velocity by 9.8 meters per second every second it falls.

Law of Universal Gravitation

Sir Isaac Newton formulated the law of universal gravitation in the 17th century.

It states that every object in the universe attracts every other object with a force proportional to their masses and inversely proportional to the square of the distance between them. 

F = (G) m1​m2​​/ r

where:

• F is the gravitational force,
• G is the gravitational constant,
• m1 and m2​ are the masses of the objects,
• r is the distance between the centers of the two masses.

Absence of Gravity

Without gravity in the universe, the consequences would be dramatic.

• No Planets or Stars: Without gravity, matter would not clump together to form stars, planets, and galaxies. 

• No orbits:  Without gravity, planets would not orbit the Sun, and moons would not orbit their planets. Instead, these celestial bodies would drift away into space in straight lines.
• No Life: Earth’s atmosphere, oceans, and rivers would all float away, making life on Earth impossible.

Fun Facts

Here are some interesting facts about gravity:

• The gravitational pull of the Moon is strong enough to affect the Earth’s tides, but it’s much weaker than Earth’s gravity.
• Black holes have such strong gravity that even light cannot escape them.
• Gravity is weaker than other fundamental forces, like electromagnetism, but it affects all objects with mass.

Review

Let’s quickly recap what we learned about gravity:

• Who formulated the law of universal gravitation? Sir Isaac Newton
• What is the acceleration due to gravity on Earth’s surface? 9.8 m/s²
• How does the gravitational force between two objects change if the distance between them remains constant but their masses increase? The force increases proportionally to the increase in mass 
• What does G represent in Newton’s Law of Universal Gravitation formula? Gravitational Constant