dynamics

• Momentum


  Product of mass and velocity of a moving object. Quantity of motion
• Momentum formula


  P = mv, unit kg·m/s or N·s
• Momentum


  • Is a vector quantity
  • Is constant if velocity is constant
  • Is constant if mass is constant
• Newton's Law of Motion

  1. First law: A body continues its state of rest or straight line motion until an external force acts on it

  2. Second law: The rate of change of momentum is directly proportional to the force applied
• Force


  The rate of change of momentum
• Newton's Third Law


  When an object A exerts a force on object B, then object B exerts the same force on object A but in the opposite direction
• Law of conservation of momentum: In an isolated system, the total momentum before a collision is equal to the total momentum after the collision
• Isolated system


  An external system in which there is no resistance force or anything
• Different cases of conservation of momentum

  • Case 1: m2 is initially at rest and after the collision, the m1 comes to rest momentarily
  • Case 2: m2 bounces from m1 which is initially at rest
  • Case 3: m1 and m2 are moving towards each other and collide and bounce back in opposite direction
  • Case 4: m1 and m2 are initially at rest and move off in opposite direction after collision
  • Case 5: m1 and m2 are moving towards each other, collide and stick together and move with common velocity
• BATE


  Elastic collision
• Elastic collision


  • Momentum as well as kinetic energy before and after the collision remain the same
• In an elastic collision, the momentum before collision = momentum after collision</b>
• In an elastic collision, the kinetic energy before collision = kinetic energy after collision
• Inelastic collision


  Collision in which momentum is conserved but kinetic energy is not before and after the collision
• Elastic collision


  • Collision of gas molecules with the walls of a container
• In an elastic collision, momentum and kinetic energy are conserved
• In an inelastic collision, momentum is conserved but kinetic energy is not
• Elastic collision


  • A ball bouncing on a floor
• In an elastic collision, the ball loses kinetic energy on each impact
• Summary of collision types

  • Elastic
  • Inelastic
• Ball A


  Mass = 0.4 kg
• Ball B


  Mass = 0.2 kg
• The collision obeys the law of conservation of momentum
• The collision does not obey the law of conservation of kinetic energy
• The collision is elastic or inelastic