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Newton’s Law of Universal Gravitation

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Newton’s Law of Universal Gravitation

Earth & Space Science

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In this activity, learners will investigate the relationship between mass and force to discover Newton’s Law of Universal Gravitation using a Cavendish apparatus.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Define Newton’s Law of Universal Gravitation as the attractive force that exists between any two objects.
  • Explain that the law of universal gravitation is directly proportional to the multiplication of the masses, and inversely proportional to the square of the distance between them.
  • Describe how the Cavendish apparatus is used to investigate the attractive force between two objects worked.
  • Explain why the Moon falls toward the Earth, like an apple falls toward the Earth.
  • Explain that Newton’s Law of Universal Gravitation is applied to all objects independent of size and position.

Everything You'll Have Covered

Newton's Law of Universal Gravitation builds upon his second law, which states that force is required to make an object accelerate. This all began with the story of Newton and the apple tree. Newton wondered what force was acting on an apple to make it accelerate toward the earth when it fell. He realized that the same force between the apple and the earth is the force of attraction that exists between any two objects in the universe.

Newton theorized in the 17th century that there is gravitational force acting between every object, and it is proportional to

The force between objects depends upon the mass of the two objects, and the distance between them. The relationship between the two masses is directly proportional to the force, so the greater the mass of one object, the stronger the force will be. The distance between the two objects also affects the force. The force is inversely proportional to the square of the distance between the two objects, so if the distance between two objects is cut in half, the force will be four times greater.

The universal gravitational constant was not able to be accurately measured however, until the 18th century when Henry Cavendish used a special devise to observe the relationship between the mass of objects and the distance between them.

The attraction between an object and the Earth can be felt when one tries to pick up a heavy object. In order to pick it up, one must overcome the attraction that the object has toward the Earth and the Earth has toward the object. This concept is what gives an object its weight.

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts Define the concept of force.Give examples of types of force.
Course Earth & Space Science
Type of Tutorial Concept Development
Key Vocabulary acceleration, attraction, attractive force