Momentum

• Momentum


  Something that all moving objects have
• Momentum


  • The greater the mass of an object, or the greater its velocity, the more momentum the object has
  • Momentum is a vector quantity-it has size and direction
• Calculating momentum


  Momentum (kg m/s) = mass (kg) x velocity (m/s)
• Momentum calculation examples


  • A 50 kg cheetah running at 60 m/s has a momentum of 3000 kg m/s
  • A 30 kg boy with a momentum of 75 kg m/s has a velocity of 2.5 m/s
• Conservation of momentum


  In a closed system, the total momentum before an event (e.g. a collision) is the same as after the event
• Conservation of momentum examples

  • In snooker, the overall momentum of the balls stays the same despite the collisions
  • When a moving car hits a parked car, the combined momentum is equal to the original moving car's momentum
• If the momentum before an event is zero, then the momentum after will also be zero
• Example of zero momentum before and after


  • In an explosion, the momentum before is zero. After the explosion, the pieces fly off in different directions, so that the total momentum cancels out to zero
• Using conservation of momentum to calculate velocities or masses

  1. Momentum before = Momentum after

  2. Rearrange the momentum equation to find the unknown velocity or mass
• Examples of using conservation of momentum to calculate velocities or masses

  • Calculating the recoil velocity of a paintball gun
  • Calculating the velocity of two skaters after a collision