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Dynamics · Physics

Forces & Newton’s Laws

Learn how forces cause (or don’t cause) motion: interactions, Newton’s laws, free-body diagrams, friction, inclines, circular dynamics, pulleys, and frames of reference.

Dynamics topics

Core topics in this track

Work through these in order for a clean Newton’s-law workflow — then practice until it feels automatic.

Start here
Forces and Interactions
What a force is, how forces come in interactions, and how to define your system.
  • Contact vs non-contact forces
  • System vs surroundings
  • Force diagrams vs free-body diagrams
Start topic Sets up everything else.
Law 1
Newton’s First Law (Inertia)
What zero net force really means, and why motion doesn’t “need a force” to keep going.
  • Inertia & inertial frames
  • Zero net force motion
  • Common misconceptions
Start topicFix the intuition.
Law 2
Newton’s Second Law (F = ma)
Turn forces into equations of motion in 1D and 2D.
  • Net force and acceleration
  • Vector nature of F and a
  • Solving equations of motion
Start topicThe main problem-solving engine.
Law 3
Newton’s Third Law
Action–reaction pairs: equal and opposite, but on different objects.
  • Correct force pairs
  • Forces on different objects
  • Examples: walking, pushing
Start topicStop the “forces cancel” confusion.
Skill
Free-Body Diagrams
Isolate one object and translate forces into equations cleanly.
  • Identify all forces
  • Choose axes
  • Write ΣF equations
Start topicYour universal method.
Forces
Types of Forces
Recognize the major forces and what they look like in FBDs.
  • Gravity, normal, tension
  • Friction, drag (conceptual)
  • When each appears
Start topicBuild your force vocabulary.
Concept
Weight vs Mass
Mass is inertia; weight is a force (and can change).
  • Weight as a force
  • Apparent weight
  • Different environments
Start topicCommonly confused.
Balance
Equilibrium and Net Force
Solve problems where ΣF = 0 (static or constant-velocity).
  • Conditions for equilibrium
  • Static vs dynamic
  • Applications
Start topicMany real structures rely on this.
Classic
Inclined Planes
Resolve forces parallel/perpendicular to the slope and solve motion.
  • Normal force on incline
  • Motion up/down
  • Inclines with friction
Start topicThe “axes choice” masterclass.
Resistance
Friction
Static vs kinetic friction and how to model them correctly.
  • Coefficients
  • Horizontal & inclined surfaces
  • Energy loss ideas
Start topicWhere many mistakes happen.
Curved motion
Circular Motion (Dynamics)
Centripetal acceleration needs a net inward force from something real.
  • Sources of centripetal force
  • Constant-speed circles
  • Banking / vertical circle intro
Start topicPreps you for gravitation & rotation.
Systems
Pulley Systems
Connected bodies, shared constraints, and tension modeling.
  • Atwood machine
  • Multiple-object systems
  • Ideal vs non-ideal pulleys
Start topicSystem thinking level-up.
Intro
Non-Inertial Frames
What changes when your frame accelerates, and why “pseudo-forces” show up (conceptually).
  • Accelerating frames
  • Pseudo-forces (conceptual)
  • Everyday examples
Start topicBuild intuition carefully.