5.9 Momentum

• What is the equation for momentum?

  p = mv
• What are the units of momentum?

  kg m/s
• What happens to the momentum of an object at rest?

  It has no momentum.
• How does momentum affect the direction of an object?

  It makes it difficult to change direction.
• Why does momentum depend on direction?

  Because velocity is a vector quantity.
• What does it mean if momentum is negative?

  The object is moving in the opposite direction.
• When does the momentum of an object change?

  When it accelerates, decelerates, or changes direction.
• What is the momentum of a tennis ball moving in the opposite direction?

  It is negative.
• What is the principle of conservation of momentum?

  Total momentum before equals total momentum after.

  
• What defines a closed system in momentum conservation?

  Absence of external forces.
• What happens to momentum in a system of objects moving towards each other?

  The overall momentum can be zero.
• What is the momentum of mass m moving with velocity u before a collision?


  m × u

  
• What happens to mass M after a collision if it was initially at rest?

  It gains momentum.
• How is total momentum calculated after a collision?

  (M × V) + (m × -v)

  
• What are the two types of collisions?

  Elastic and inelastic collisions.

  
• What occurs in an elastic collision?

  Objects move in opposite directions.
• What occurs in an inelastic collision?

  Objects move together in the same direction.
• What must be true for momentum to be conserved in a collision?

  Momentum before equals momentum after.

  
• What is the role of safety features in vehicles regarding momentum?

  They increase contact time to reduce force.
• What are the main vehicle safety features?

  Crumple zones, seat belts, airbags.
• How do crumple zones work?

  They absorb energy by changing shape.
• What is the purpose of seat belts?

  To keep passengers fixed during abrupt stops.
• How do airbags help in a collision?

  They cushion the impact for passengers.
• What do crash mats do in gymnasiums?

  They absorb shock to reduce injury risk.
• Why are thicker crash mats used for higher falls?

  To increase contact time and reduce force.
• What is the effect of mass and velocity on safety equipment effectiveness?

  Higher mass and velocity require longer contact time.
• Can safety features completely prevent injury?

  No, they reduce but do not eliminate risk.