5. Identifying Forces

Given seven drawings depicting motion, students will be able to correctly identify, describe, and indicate direction and relative magnitude of three to five forces in each.

Relationship to big idea
Everything physical in the universe is affected by forces.  These forces cause (or stop) motion.  In this lesson, students identify specific examples of forces acting in various situations.

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?

Students complete a bell work assignment reviewing the definition of forces on previous lesson's graphic organizer.  They may use the organizer and/or book to complete the task.

Read directions for task: Students need to identify the force described and draw an arrow showing its size and direction.  All of the forces described are also on their "Types of Forces" notes.

Demonstrate example item for students.  Read description of each force and walk students through process of comparing description to definitions of forces on notes.  Model placement and size of arrows representing forces on diagram.

Check for understanding
On first item, read description and have students check description against definitions on notes.  Students share and defend answer with group, then class chorally responds to report appropriate force (compression).  Ask students if they have finished the task (no) and what to do next (draw arrow on diagram).  

Guided practice
Students complete item 1, working with their groups; review as a class.  Students chorally respond with names of forces described and individuals describe direction of arrow.  Students complete remainder of items with their groups while teacher circulates, checking work.

On a quarter-sheet of paper, students sketch a situation described by the teacher: You push in your chair to leave the room.  Students identify three forces acting on the chair in this situation and draw labeled arrows to show the direction.  The quarter-sheet is their ticket out the door.

Approaches and instructional strategies
Cooperative learning: Groups work on demonstrating cooperative behaviors (take turns, use each other's names, encourage everyone to participate)

Productive questioning: As groups work, teacher asks students reasoning questions.  (Why do you think the example describes ___ force?  Can you invent a rule to describe situations involving static friction?)