momentum

• Momentum


  A quantity relating to a moving object that is calculated by multiplying its mass by its velocity
• Momentum


  • It is a vector quantity - it has both magnitude and direction
• Momentum can be calculated using the equation: momentum = mass × velocity
• Momentum (p)


  Measured in kilogram metres per second (kg m/s)
• Mass (m)


  Measured in kilograms (kg)
• Velocity (v)


  Measured in metres per second (m/s)
• Example


  • A lorry has a mass of 7,500 kg and travels south at a speed of 25 m/s. The momentum of the lorry is 187,500 kg m/s (south).
• Question


  • An ice skater has a mass of 60 kg and travels at a speed of 15 m/s. The momentum of the skater is 900 kg m/s.
• Momentum


  A combination of mass and velocity
• Momentum helps explain some of the most important interactions in nature
• Conservation of momentum


  • In a closed system: total momentum before an event = total momentum after the event
  • The principle that the total momentum of a system remains the same
  • When bodies collide, whatever momentum is lost by one body, the other gains in equal amounts
• Closed system


  Something that is not affected by external forces
• When a cannon is fired

  The cannon ball gains forward momentum and the cannon gains backward momentum
• Before the cannon is fired, the total momentum is zero because neither object is moving
• The total momentum of the cannon and the cannon ball after being fired is also zero, with the cannon and cannon ball moving in opposite directions