Change in momentum

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Change in momentum
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Impulse

• In order to change the momentum of an object, an
  impulse must be applied to it.

3
Any moving object has momentum
m
v

• The magnitude of the impulse applied to the
  object, will equal the objects change in momentum

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What is the difference between impulse and change
in momentum?

• The equation above does not mean that impulse and
  change in momentum are the same thing.
• It says that their amounts are the same.

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Change in momentum by definition is
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The impulse applied to an object will equal the
objects change in momentum
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When jumping, why will it be less painful if you
flex your body when you land?
Therefore,

• The force applied to your body is inversely
  proportional to the stopping time.

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Conservation of momentum
M100 kg
V10 m/s
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The total momentum before collision must equal
the total momentum after collision
to the right
100

• Notice that to the right is positive and to the
  left is negative

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In order to conserver momentum, after collision,
the total momentum must be
to the right
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Conservation of momentum

• Since the force on the bullet and gun must be
  equal in magnitude and are applied for the same
  length of time, the impulse must have the same
  magnitude for both.

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Impulse change in momentum

• Because the gun and bullet have the same impulse
  applied to them, they must have the same change
  in momentum

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Conservation of momentum

• The change in momentum for the Terminator must be
  the same as the change in momentum of the shooter.

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Why does landing on the air bag help to prevent
death
Impulse change in momentum
Therefore

• The air bag provides a longer stopping time and
  therefore a smaller force is applied to the
  jumper.

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How does a padded dash help to prevent injuries?
Impulse change in momentum
Therefore

• The padded dash provides a longer stopping time
  and therefore a smaller force is applied to the
  jumper.

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Long barrel results in a larger time which will
produce a larger change in momentum
Impulse change in momentum

• When you change the momentum of an object, you
  change its velocity

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Why didnt the professor move backward as fast as
the marble moved forwad?

• The change in velocity is inversely proportional
  to the objects mass.
• The professors mass was much larger than the
  marbles, so he had a tiny change in velocity.

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Is momentum conserved when a bullet is fired from
a gun?
Vbullet
Mgun
Vgun
mbullet
Magnitude of Pgun
Pbullet

• Yes
• Their masses and velocities are different, but
  their change in momentum will be equal in
  magnitude and opposite in direction

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Why can a karate punch apply a large force?
Therefore

• Because of the small stopping time

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As the stopping time approaches zero, the force
approaches infinity

• Notice the inverse relationship between the time
  and the force