Changes in Motion

Edit Note  |  Creator:  sliao082

Newton's Laws


  • 1st law: objects are either at rest of moving with constant velocity as long as no net force acts on it (law of inertia)

  • 2nd law: F=ma (single force) → ΣF=ma (net force cause the acceleration)

  • 3rd law: For every action force acting on an object, there is a reaction force acting on a different object, and they are equal in magnitude and opposite in direction

Free Body Diagram


  • Once all of the forces are drawn on a free-body diagram, a coordinate system is chosen and each force is resolved into components

Methods for Free-Body Diagram


  • Force type: contact / super

  • Frictionless: only normal force (perpendicular to the surface)

  • One surface (point): one contact force

  • The direction of soft / hard object ≠ the direction of force

  • Soft object: rope, string / Hard object: stick

  • Count the amount of forces

  • Force resolving parallel / perpendicular the direciton of motion