Momentum

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Momentum Key Ideas
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Review If a force Fx is applied to a body over
a displacement Dx, the product Fx Dx (Fcosq)Dx
Work
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Review If a force Fx is applied to a body over
a displacement Dx, the product Fx Dx (Fcosq)Dx
Work If the friction force is less than Fx,
the work increases the objects Kinetic Energy
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NOW ask What is the effect of applying a force
over a time interval? Vocabulary events in
which objects apply forces to each other are
called INTERACTIONS
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NOW ask What is the effect of applying a force
over a time interval? Vocabulary events in
which objects apply forces to each other are
called INTERACTIONS You predicted the outcomes
of some interactions.. How did you do?
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You predicted the outcomes of some interactions..
How did you do? A general rule about
interaction forces
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A general rule about interaction forces
Forces come in
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A general rule about interaction forces
Forces come in
This is Newtons 3rd Law.
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Impulse Change of momentum
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Impulse Change of momentum
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The impulse is the area under the force vs. time
curve. The average force gives the same impulse
to the object in the time interval ?t as the real
time-varying force.
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Conservation of Momentum
The principle of conservation of momentum states
when no external forces act on a system
consisting of two objects that collide with each
other, the total momentum of the system remains
constant in time.
Specifically, the total momentum before the
collision will equal the total momentum after the
collision.
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Conservation of Momentum
Mathematically
Momentum is conserved for the system of
objects. The system includes all the objects
interacting with each other. Assumes only
internal forces are acting during the
collision. Can be generalized to any number of
objects.
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Force as a function of time for the two colliding
particles.
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• In all collisions,
• total momentum is conserved.
• We consider two types of collisions in one
  dimension
• Totally elastic
• Totally inelastic

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Perfectly Inelastic Collisions
When two objects stick together after the
collision, they have undergone a perfectly
inelastic collision. Conservation of momentum
becomes
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Elastic Collisions Both momentum and kinetic
energy are conserved.