Forces and interactions
What students will learn
Choose a system, identify its interactions, and use force diagrams to explain equilibrium or acceleration.
Before this topic
- Motion and vector components
- The distinction between velocity and acceleration
Read and connect
Read: Systems and Center of Mass →
Choose the system boundary and locate a mass-weighted center of mass.
Read: Forces and Free-Body Diagrams →
Draw the actual interactions on one object and write component equations.
Read: Newton’s Third Law →
Keep Newton’s third-law partners on separate objects and identify internal forces.
Read: Newton’s First Law →
Recognize force balance in both stationary and constant-velocity systems.
Read: Newton’s Second Law →
Connect the external force sum to center-of-mass acceleration.
Read: Kinetic and Static Friction →
Choose static or kinetic friction from the motion at the contacting surfaces.
Read: Spring Forces →
Measure spring deformation from relaxed length and distinguish spring force from net force.
Check understanding
Use the complete prompt to make student reasoning visible, then consult the separate worked reasoning and criteria. A reading completion tick records reading history.
Build a force model on a rough incline →
Choose axes, draw real forces, and write both component equations without assuming constant speed.
Test a spring-force graph →
Infer stiffness with units and propose a measurement that could reveal departure from the linear model.
Standards and earlier reading lists
These topic placements organize reading. Edition-qualified Standards mappings and the existing complete unit task sets retain their reviewed scope.