Newton's Laws and Momentum

Newton's Laws and Momentum

1. Momentum and Impulse

   • momentum = mass x velocity
   • Momentum is always conserved
     • total mu = total mv
     • Even in inelastic collisions
       • In elastic collisions kinetic energy is conserved, it isn't in inelastic ones
   • Impulse is a change in momentum
   • F = (mv-mu)/t
     • Ft = mv - mu
     • I.e. in crumple zones were t is increased F is decreased

2. Newton's Laws of Motion

   • 1st Law - A force is needed to change velocity
     • If the resultant forces aren't balanced, then an object will accelerate
   • 2nd Law - Force is the rate of change in momentum (F=ma if the mass is unchanging)
     • The resultant force is the vector sum of all forces and acceleration is always in the same direction as the resultant force
   • 3rd Law - If object A exerts a force on object B, then object B exerts an equal but opposite force on object B