**Physics Classroom: Recognizing Forces**

Before students can reasonably be expected to understand force pairs, it helps if they can identify forces! This interactive problem set is designed to help students recognize forces that are exerted in 11 common physical situations. For each situation, the student will decide which forces are present (P) or absent (A), then use a pull-down menu to view correct answers.

**University of Tennessee: Newton's 3rd Law Tutorial**

Here's a straightforward tutorial that presents Newton's Third Law in the context of force interactions. It features six problems of varying degrees of difficulty. The author explains in detail how to construct a free-body diagram for each situation, then provides explicit solutions to each problem.

*Editor's Note: Although this tutorial is not inquiry-based, students sometimes need to approach novel or counterintuitive concepts through concrete examples. This resource provides such scaffolding.***Illinois PER Interactive Examples: Two Masses on a Table Edge**

This interactive problem for introductory physics features two blocks of differing mass connected by a string over an ideal pulley located at the edge of a table. Students must determine the magnitude of acceleration on Block B, given the length of the string and the mass of each block. The author carefully takes learners step-by-step to determine the forces acting on each block in both the x and y directions. A user-activated "help" sequence is provided for each step of the problem-solving, including conceptual analysis, free-body diagrams, and help with calculations. Immediate feedback is received for both correct and incorrect responses.