Activity 3: Newton’s Law of Universal Gravitation
(SI GLEs: 2, 12, 19, 25, 27, 28, 34; PS GLEs: 5, 6) 
Materials List: teacherselected reading material about Galileo Galilei, books for research or Internet access, postersize paper, string or yarn, index cards, computer projector, optional software for concept map
Part A: Have the students compare and critique scientific investigations of Johannes Kepler, Tycho Brahe, Galileo Galilei, and Nicholas Copernicus. Kepler theorized that planets closest to the Sun moved faster than those farther away. However, it was Isaac Newton that finally explained Kepler’s theory. Newton’s Law of Universal Gravitation states that the force of gravity depends on the product of the masses of the objects divided by the square of the distance between them. If two objects have a mass of 1kg and are moved twice as far apart, the gravitational attraction between them will decrease by a factor of ¼. How can something you multiply (factor/times) show a reduction? This is because of the division by the square of the distance: F_{grav}= (m_{1} x m_{2}) / d^{2}, where F_{grav}= the force of gravity between the two objects, m_{1} and m_{2 }are the two objects’ masses, d is the distance. As in the previous example, (1kg x 1kg) / 2^{2} = ¼ the force of gravity. Challenge the students to calculate how much of a gravitational decrease would occur if the same objects were moved 10 times farther apart (10 x 10 = 100 times less than the original force of gravity).
Challenge the students to work cooperatively to solve the following separate problems. “If you could increase Earth’s mass by two times, how much gravitational influence would Earth have on an orbiting satellite?” (twice as much) “If the satellite is boosted three times farther from Earth, would the gravitational pull on the satellite be more or less?” (less) “How much of a difference would there be?” (3 x 3 = 9 times less than the original force of gravity).
For closure, have students form groups of three or four to construct a concept map, a graphic organizer (view literacy strategy descriptions), of gravity. Provide students with postersize paper, string or yarn, and cards that have key terms and phrases as well as blank cards for studentgenerated terms and phrases. If software programs for concept maps are available, students can construct their concept map using a computer and the program. Students should be able to print these. Allow a twominute talk for each student group to share their concept map with the class. Students’ concept maps could be displayed in the classroom. 
Lessons/Resources:
 Vocabulary Self Awareness
 Gravity Pete's PowerPoints
 Force/Motion Pete's PowerPoints
 Leaning Tower of Pisa  Click on Galileo’s name for the story. Next, click on the picture for a virtual lab and display it for the entire class to view.
 NASA QuickTime video showing the feather and hammer experiment on the moon
 Newton's Laws Pete's PowerPoints
 Famous People: Sir Isaac Newton  eThemes  eMINTS
 Physics: Force and Motion  eThemes  eMINTS

Understanding Newton’s Laws Lesson Plan, Motion, Inertia, Force Pairs, Worksheet, Teaching Activity & Lesson PDF File
 Newton's Laws of Motion Table of Contents

 Newton's Three Laws of Motion

Motion and Forces

Lab Work/Lab Safety (Pete's PowerPoints)

The Scientific Method (Pete's PowerPoints)

8th Grade Science Comprehensive Curriculum Document

Blackline Masters

18 Literacy Strategies Student Interactives

Graphic Organizer Interactives

Recording Tools (Graphs, Timelines, Graphic Organizers, Recording Tools, Investigation Tools)

Additional places contracts can be found

Comparison of proper and improper lab practices
Interactives:
Websites:
