Free body diagrams

• Examples of Forces

  • When forces act on an isolated body or system they can be represented as vectors
  • These vectors can be added together to work out resultant forces to determine the motion of the body or system
  • For example: 
  • The forces acting on a body in freefall are weight (downwards) and drag (upwards). This body will reach terminal velocity when these two forces are balanced
  • The forces acting on an aircraft are thrust (forwards) drag (backwards) lift (upwards) and weight (downwards). The engine can control the amount of thrust, and the tilt of the wings can control the lift
• Free Body Diagrams

  • Free body diagrams are useful for modelling the forces that are acting on an object
  • Each force is represented as a vector arrow, where each arrow:
  • Is scaled to the magnitude of the force it represents
  • Points in the direction that the force acts
  • Is labelled with the name of the force it represents
  • Free body diagrams can be used:
  • To identify which forces act in which plane
  • To resolve the net force in a particular direction