Newton’s Third Law

Newton’s Third Law: An introductory activity.

1) Begin with Demonstration (video taping can help):

a) Have two students (similar in size and mass) sit in identical wheeled chairs. Ask students to give each other a push.

b) Class writes down observations. (Allow measurements to be taken by class if asked.)

c) Both students face each other again. Student A locks elbows, Student B pushes.

d) Class writes down observations.

e) Repeat steps 1-4 with students who differ greatly in size and mass.

2) Organize students into groups of 3-4.

3) Pose Problem (Allow groups 3-4 minutes to discuss possible answers.):

What force(s) pushed student B during the second trial?

4) Focus/guide students into a problem solving plan. Have each group:

Come up with a testable hypothesis.
The hypothesis should include force diagrams.
Come up with a plan for testing the hypothesis.
If necessary, adapt test so that the test can be conducted in the classroom with available supplies.

5) Test hypothesis. Use materials supplied by teacher.

6) Research other’s findings.

In the case of this experiment, it will be simply finding out how Newton described the phenomena.

7) Communicate findings.

Have each group come up with a brief written statement to include the following:
Describe your hypothesis, test, and results.
Back up or refute hypothesis with results.
Back up or refute hypothesis with the following translation from Newton’s Principia:

To every action there is always opposed an equal reaction; or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts. http://members.tripod.com/~gravitee/axioms.htm

Sample Homework problems:

Have students survey 2-3 friends and/or family members outside of class. Describe observations of beginning demonstration. Ask subject for a brief explanation of the observations.