Ch. 9 Momentum and Its Conservation

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Ch. 9 Momentum and Its Conservation

• Milbank High School

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Sec. 9.1Impulse and Momentum

• Objectives
• Compare the system before and after an event in
  momentum problems
• Define the momentum of an object
• Determine the impulse given to an object
• Recognize that impulse equals the change in
  momentum of an object

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Momentum

• What is momentum?
• The Minnesota Vikings have momentum entering the
  final weeks of the season
• Anything that is moving
• has momentum
• Depends on what?

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Momentum

• Momentum mass velocity
• In physics, the symbol for momentum is p
• sssooo
• p m v
• kgm/s
• Which has more momentum, a supertanker tied to a
  dock or a raindrop falling?

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Momentum

• Determine the momentum of a ...
• 60-kg halfback moving eastward at 9 m/s.
• 60 x 9 540 kgm/s east
• 1000-kg car moving northward at 20 m/s.
• 1000 x 20 20,000 kgm/s
• 40-kg freshman moving southward at 2 m/s.
• 40 x 2 80 kgm/s

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Impulse and Momentum

• Impulse Change in momentum
• Impulse
• The product of the average net force exerted on
  an object and the time interval over which the
  force acts
• Ns

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Real Life Applications..

• Sports
• Follow-through!
• Gymnastics Mats
• Cars
• Airbags!
• Before airbags.
• Bumpers
• Eggs
• Jumping
• Knees
• Shoes

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Review

• Can a bullet have the same momentum as a truck?

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Sec. 9.2The Conservation of Momentum

• Objectives
• Recognize the conditions under which the momentum
  of a system is conserved
• Apply conservation of momentum to explain the
  propulsion of rockets
• Solve conservation of momentum problems in two
  dimensions by using vector analysis

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The Law of Conservation on Momentum

• The total momentum of two objects before a
  collision is equal to the total momentum of the
  two objects after the collision.

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Two Particle Collisions

• Inelastic collisions
• mAvA1 mB1vB1 mAvA2 mBvB2

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Propulsions

• We can also use
• pA2 -pB2
• mAvA2 -mBvB2
• Example Problem Pg. 212