NSTA Press publishes high-quality resources for science educators. This series features just a few of the books recently released. The following excerpt is from Companion Classroom Activities for Stop Faking It! Force & Motion, by William Robertson with illustrations by Brian Diskin, edited for publication here. Download the full text of this chapter. NSTA Press publications are available online through the NSTA Science Store.
Objectives. The students will be able to provide a complete description of Newton’s first law. The students will be able to define the word inertia, which is a property of objects and describes their tendency to obey Newton’s first law.
Process Skills Addressed. analyzing, inferring
National Science Education Standards Addressed. Content standard B: Position and motion of objects; Properties and changes of properties in matter, Motion and forces. Content standard G: History of science.
Position in the Learning Cycle. Explain. The students read an explanation of the activity they did in Objects in Motion, learn a complete explanation of Newton’s first law, and learn the meaning of the word inertia. You discuss these things with the class.
Suggested Group Size. individual and whole class
Materials. Copies of the student reading
Approximate Time. 30–40 minutes
- Have the students read Galileo Explains It All. This reading is reasonably long, so encourage the students to take their time getting through it. Younger students will need considerable help with the passage, and you might choose to explain the concepts verbally rather than have them read on their own.
- Discuss the reading with the class. Important points:
*Be sure they understand the connection between the activity they did and Galileo’s reasoning that objects moving in a straight line will continue to do so. The students have to buy into the following statements before they can make the connection: The marble stops and turns around when it reaches a certain height. It never reaches that height because the track is completely flat forever and ever. So it never stops.
*The claim that Galileo invented the force of friction might bother the students (and you!). This is really a philosophical position that not everyone will buy into. Before Galileo’s time, Aristotle’s view of the world was generally accepted, and Aristotle believed that objects naturally came to rest, with no need for a force to cause that. In fact, Aristotle believed that forces were required to keep objects moving. This completely contrasts with Galileo’s view, but you might notice that Aristotle’s view makes a whole lot more sense in terms of everyday experience! Acknowledge to the class that sometimes science concepts, on first exposure, do not seem to apply to everyday experience. What matters in the end is that things like Newton’s first law work, and that these laws explain what happens around us.
*Inertia is a property of objects. It simply describes the tendency of objects to keep on doing whatever they’re doing. Inertia is not a force, but no need to dwell on that at this point. This will be addressed in later activities.
*Forces are what change the motion of objects. A more precise statement would be that forces change the velocity of objects. That the changes in motion we’re dealing with are actually changes in velocity is addressed in another activity. No need to overwhelm the students in this one reading.
*It is more correct to say that net forces cause changes in velocity, but again, no need to overwhelm the students right now. The concept of net force will be addressed later.
- End the discussion by asking the students to give examples of objects with a lot of inertia and objects with very little inertia. Examples are given in the student reading, but try to get the students to go beyond those specific examples and suggest objects they come in contact with every day.
*Objects with little inertia. balloons, pinecones, marbles, and feathers
*Objects with lots of inertia. a piano, an anvil that falls on Wile E. Coyote, a cement truck, and the school building