In Chapter 1, we focused on energy transfers due to heat; here, we explore transfers due to work, requiring an understanding of force. Extending the Energy-Interaction Model to mechanical interactions...In Chapter 1, we focused on energy transfers due to heat; here, we explore transfers due to work, requiring an understanding of force. Extending the Energy-Interaction Model to mechanical interactions, we define force as a vector with magnitude and direction. We distinguish between contact forces and long-range forces, like gravity. Understanding balanced versus unbalanced forces helps analyze how forces cause or prevent motion, setting up a foundation for studying work and energy change.