The Universal Law of Gravitation - Part 1 | Physics | Don't Memorise

Summary

This video explains the concept of gravitational force and how it acts between two objects. It clarifies that both the Earth and an apple apply equal gravitational force on each other, but due to the Earth's massive size, the apple accelerates toward it. The Universal Law of Gravitation is introduced, stating that gravitational force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between them. The formula for this force includes the Universal Gravitational Constant (G), whose value was discovered by Lord Henry Cavendish.

Takeaways

• 🌍 The gravitational force is an attractive force between any two objects with non-zero mass separated by a distance.
• 🍎 Both the Earth and the apple exert an equal gravitational force on each other, but the apple accelerates more due to its smaller mass.
• ⚖️ According to Newton's second law, acceleration is inversely proportional to mass, meaning objects with less mass accelerate more for the same force.
• 📏 The Universal Law of Gravitation states that every object attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
• 🔢 The gravitational force (F) can be written as: F = G * (m1 * m2) / d², where G is the gravitational constant.
• 🧲 G is the Universal Gravitational Constant, which is experimentally determined to be 6.673 × 10⁻¹¹ N·m²/kg².
• 🧪 Lord Henry Cavendish discovered the value of G using a torsion balance experiment.
• 📐 The units for G are derived as N·m²/kg² based on the units of force (Newtons), distance (meters), and mass (kilograms).
• 🔗 As the distance between two objects increases, the gravitational force decreases due to the inverse-square relationship.
• 🚀 If the mass of either object increases, the gravitational force between them also increases.

Q & A

What is the gravitational force?

The gravitational force is the attractive force between any two objects with non-zero mass, separated by a distance.

Does the Earth move towards the apple or does the apple move towards the Earth?

Both the Earth and the apple apply an equal gravitational force on each other, but due to the much larger mass of the Earth, the apple accelerates more towards the Earth.

Why does the apple accelerate more than the Earth if both apply equal forces?

According to Newton's second law, acceleration is inversely proportional to mass. Since the Earth's mass is much greater than the apple's, the apple experiences much more acceleration.

What is the Universal Law of Gravitation?

The Universal Law of Gravitation states that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

How is the gravitational force between two objects calculated mathematically?

The gravitational force is calculated as F = G * (m1 * m2) / d², where G is the universal gravitational constant, m1 and m2 are the masses of the two objects, and d is the distance between their centers.

What is the value of the universal gravitational constant (G)?

The value of G is 6.673 × 10⁻¹¹ N·m²/kg².

How does the distance between two objects affect the gravitational force between them?

The gravitational force decreases as the distance between two objects increases, specifically, it is inversely proportional to the square of the distance.

Who determined the value of the universal gravitational constant?

The value of the universal gravitational constant was determined by Lord Henry Cavendish using a torsion balance.

What are the units of the gravitational constant (G)?

The units of G are N·m²/kg², where N is newtons, m is meters, and kg is kilograms.

What happens to the gravitational force if the mass of one object increases?

If the mass of one object increases, the gravitational force between the two objects also increases, as the force is directly proportional to the product of the masses.