mechanics and mechanical injury

• displacement is a 


  vector quantity
• distance is a


  scalar quantity
• velocity 


  rate of change of displacement
• acceleration 


  rate of change in velocity
• deceleration 


  when velocity reduces
• Newton's first law of motion

  an object will remain in motion unless acted upon by an external force
• Newton's second law of motion

  a force is any action that alters, or tends to alter a body's state of rest or of uniform motion in a straight line
• Newton's third law of motion

  for every action, there is an equal and opposite reaction
• inertia


  the tendency to remain in an initial velocity state
• effective weight 


  a modified or adjusted weight that considers additional factors such as buoyancy, support or additional factors
• energy 


  capacity or ability to do work
• kinetic energy 


  comes from movement
• potential energy 


  comes from position
• conservation of energy


  energy cant be created or destroyed, just transformed from one form to another
• law of conservation of momentum 


  momentum is neither created nor destroyed, but only changed through the action of forces
• interaction times are increased by

  collapsible steering columns, padded interiors, crumple zones, airbags, head/side impact protection systems, airbag vests
• coefficient of friction 


  a measure of the amount of friction between two surfaces
• whiplash 


  skull has considerable inertia, meaning when a car stops suddenly the rest of the body is stopped by the seatbelt and the skull is flung forward, causing whiplash
• active head restraints


  used to prevent inertia