Overview

In this activity, two problems which are similar but have an important difference are assigned to groups. In this case, both groups must find the force of friction between two blocks (one on top of the other) as well as the applied force. In one case, however, both blocks accelerate together, whereas in the second the upper block is tied to a wall behind them.

Each group works on their problem (at a whiteboard or SMART board). Before any group can finish, the instructor calls on the students to switch whiteboards or SMART boards with a group working on the ...

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In this activity, two problems which are similar but have an important difference are assigned to groups. In this case, both groups must find the force of friction between two blocks (one on top of the other) as well as the applied force. In one case, however, both blocks accelerate together, whereas in the second the upper block is tied to a wall behind them.

Each group works on their problem (at a whiteboard or SMART board). Before any group can finish, the instructor calls on the students to switch whiteboards or SMART boards with a group working on the other problem. Groups must identify the difference and determine how it will alter the way in which the problem must be approached. They then evaluate the other group's work, correcting any errors, and complete the second problem.

Time permitting, the groups return to their original problem and determine whether or not they agree with the second group's solution. After the problems have been completed, the instructor reviews the solutions, paying close attention to the differences between the two problems, to the errors which led to incorrect solutions, and to different approaches to each problem.

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Objectives

Students will learn to apply Newton’s second and third laws to problems involving friction between multiple objects. Students learn to identify key distinctions between similar problems.

Context and requirements

Level Grade 12-U0
Discipline Physics
Course Mechanics
Activity Content Friction, Newton's Second Law, Newton's Third Law
Technological Requirements Whiteboards or interactive whiteboards.
Best Use Practice, Review

Author’s Notes

Benefits

This activity exposes students to variations of a typical problem in a shorter amount of time than it would take to cover both problems. Students are forced to analyze the work of other students in order to continue, and to contrast superficial details between the two problems. When the problems are side by side, students can easily see the difference between the two and how it affects the question.

Challenges

Choosing problems at the right level is difficult, and choosing incorrectly can cause problems in pacing – students should advance at a similar pace. You need to choose problems that are hard enough that no group finishes it right away, but also not so hard that no groups finish the problem.

Tips

Try to avoid getting involved too early. Students will have questions, but you should allow them to struggle and make mistakes so that other groups can then catch these mistakes. If no errors are made, there is much less point to this activity.

Obviously you should ensure that no team is able to finish before you do the first rotation: keep careful track of how far your more “advanced” groups have gotten.

Activity Pedagogical Components

Problem Solving

Working in GROUPS, students begin a physics problem at a whiteboard or other work station. This work is completed IN CLASS.

Peer Review

Before any group can complete their problem, students switch whiteboards with a group working on a similar but different problem. In GROUPS, students peer review the other group’s work, making corrections and annotations. This work is completed IN CLASS.

Distributed Problem Solving

In GROUPS, students complete the second problem. This work is done IN CLASS.

Peer Instruction

Students return to their original whiteboard. In GROUPS, they determine whether they agree with the corrections and solution proposed by their peers. This task is done IN CLASS.

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