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Understanding Newton's Law of Gravity

By Kathy Foust

Use this lesson plan on Newton's Law of Gravity to teach your students about the concept of gravity and how the law of gravity works. Add this science lesson plan to your collection of gravity lesson plans today and make use of the study guide that accompanies it as well!

Introduction to Gravity

Physical science students may balk at the idea of learning about gravity, since they already probably have a preconceived notion about what gravity is. The trick will be in presenting gravity lesson plans to them in a new and entertaining way, which isn't too difficult when you consider the nature of the law of gravity.

  • Begin by asking students what is the largest object in the solar system as we know it? Hopefully a student will come up with the Sun as the answer. If not, explain to students that the Sun is the largest object in the universe.
  • Explain Newton's Law of Gravitation to your students as follows: Every particle in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
  • Translate Newton's Law of Gravity to explain that the closer and larger two objects are, the more they are attracted to each other. Another way to put it is that two large objects that are close together are going to have more magnetism toward each other than two small objects sitting far apart.
  • Ask students to ponder why, if the Sun is the largest object in the universe, are we not just drawn straight into the Sun instead of the Earth.
  • Explain to students that we are attracted to the Earth because the Earth is the largest object close to us. In turn, the Earth has an attraction to the Sun, thus it orbits the Sun.

Newton's Law of Gravity and Planets

Ask students the following questions and have them explain their ideas based on Newton's Law of Gravitation.

  • Based on Newton's Law of Gravitation, why is the gravity on the moon so different from the gravity on the Earth?
  • If there is another planet with a larger mass than the Earth and it originally started at a distance from the moon equal to the distance that the Earth is from the moon, would the moon revolve around the Earth or the other planet?
  • What is the difference between mass and weight and how does gravity effect it?

After reviewing the above questions with your students, refer them to the Newton's Law of Gravity Study Guide to reinforce their understanding of gravity and to learn about Newton's Law of Gravity as it is understood in mathematical form.