Momentum and Inertia

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Momentum and Inertia
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Momentum

• Momentum mass x velocity
• MV P
• Momentum is inertia in motion.
• A moving object has more p than an object with
  less m.
• An object at rest has no p (v 0)

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Momentum

• If the p of an object changes, the m, v, or both
  MUST change.
• If the v changes, then the object is accelerating
• a produces F
• The greater the F, the greater the change in v

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Impulse

• The F sustained for a longer period of time
  produces more ?p.
• This relationship of F to t is called impulse.
• Impulse F?t
• The greater the impulse, the greater the ?p.

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Impulse-Momentum relationship

• F?t mv
• This relationship helps us to analyze situations
  where the p changes.

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Bouncing

• When an object bounces off a surface, the impulse
  is greater.
• The impulse required to bring an object to a stop
  and then to throw it back again is greater than
  the impulse required merely to bring it to a
  stop.

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Conservation of Momentum

• If you wish to change p, you must exert an
  impulse on it.
• The impulse must be exert on the object by
  something outside the object.
• When a cannon is fired, according to Newtons
  3rd, the ball has an equal but opposite force to
  the cannon.
• Same thing with p (within the system of the
  cannon and the ball)the overall p before and
  after do not change.

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Conservation of Momentum

• Remember p is vector quantity (magnitude AND
  direction)
• If no net force or net impulse act on a system,
  the momentum of that system cannot be changed.
• Law of Conservation of Momentum
• In the absence of an external force, the momentum
  of a system remains unchanged.

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Collisions

• The collision of objects clearly shows the
  conservation of p.
• Net momentum before collision
• Net momentum after collision
• Two main types of collisions
• Elastic and inelastic

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Elastic Collisions

• Elastic collision
• When objects collide without being permanently
  deformed or without generating heat.
• Ex billiard balls (pool) swinging balls
  apparatus
• The momentum from the first object is transferred
  to the second object (or vice versa).

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Inelastic Collisions

• Inelastic collisions
• When colliding objects become entangled or
  coupled together, thereby generating heat or
  disfigurement.
• The net p before the collision equals the net p
  after the collision
• Net (mv) before collision Net (mv) after
  collision