4. Types of Forces

Objective
Given a textbook passage on forces, students will be able to organize the passage's information into a graphic organizer and teach the information to other students.

Relationship to big idea
Everything physical in the universe is affected by forces.  These forces cause (or stop) motion.  In this lesson, students learn the scientific names and description of some forces.

Contribution to student understanding
The lesson helps students understand how the combination of forces affects the motion of objects.

Essential question
How do multiple forces on an object affect the object's motion?

Set
Students complete a bell work assignment identifying descriptions of forces (dragging your shoe on the ground, an apple falling to the earth) as "friction" or "not friction," based on what they saw in the previous lesson (baby shoes lab).  

Input
Explain that the previous lesson's lab explored the force of friction.  Friction isn't the only type of force - any push or pull is a force, and many of them have scientific names.  The scientific names of the forces students will read about today are: gravity, weight, tension, compression, friction, static friction, sliding friction, and air resistance.  Students will each read about two forces, complete their section of the organizer, and report back to their group.

Model
Demonstrate how to fill out the chart for students, using different sections for each force.  Walk students through process of identifying key words for the section and locating them or synonyms in the text.  (For example, when searching for the direction of the force, students might look for the words "direction," or "acts in.")

Check for understanding
Students summarize task in pairs.  Individual volunteers report task components to teacher; teacher lists tasks in order on board.

Guided practice
Students complete organizer for first task in small pieces, guided by teacher.  ("Find the definition of your first force in the book.  Now, put it into your own words.  Draw a picture showing an example of the force or describing the force.")  Students complete remainder of items with their groups while teacher circulates, checking work.

Students summarize the information they read to members of their group.  Summary takes the form of one sentence per section - students receive a template to follow.  

  • _____ is _____.
  • I drew ____ because ____.
  • _____ acts on _____ objects.
  • The direction of _____ is _____.
  • _____ is affected by _____.

("Gravity is a force pulling objects together.  I drew ___ because ___.  Gravity acts on all objects, even if they aren't touching.  The direction of gravity is toward the other object.  Gravity is affected by the mass of objects and their distance from each other.")  

Closure
Teacher reads definition of forces.  Students check their notes, confer with groups, and chorally report the type of force described.

Approaches and instructional strategies

Cooperative learning: Task uses positive resource independence.  Groups work on demonstrating cooperative behaviors (use each others names, listen accurately to what others are saying, critique ideas, not people).

Productive questioning: As students work, teacher asks individuals questions.  (How is your first force like your second force?  How are they different?  What happens to the force of gravity if you move the objects farther apart?  What would happen if there were no static friction?  What is your reason for that drawing?)

Reciprocal teaching for reading comprehension: Modeling of comprehension strategies