Momentum is a measure of inertia in motion. Momentum is equal to mass multiplied by velocity. p = mv

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Momentum is a measure of inertia in motion.
Momentum is equal to mass multiplied by
velocity. p mv
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A 2250 kg pickup has a velocity of 25 m/s east.
What is the momentum of the truck?
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A moving objectcan have a large momentum if it
has a large mass, a high speed, or both.
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Can you think of a case where a roller skate and
a truck would have the same momentum?
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If momentum changes, either the mass of the
object or its velocity or both change.
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In most cases the velocity changes, not the
mass. A change in velocity is acceleration,
which is caused by only one thing
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an unbalanced force. The greater the force,
the greater the acceleration and the greater the
change in momentum.
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The length of time the force is applied is also
important. The longer the force is applied the
greater the change in momentum.
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Force times time interval is called impulse.
Impulse Ft
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Remember F ma, and a ?v/?t.Therefore
F m ?v/?t, or F?t m?v
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F?t m?v, or Ft ?mvImpulse is equal to
change in momentum.
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A 1400 kg car moving west with a velocity of 15
m/s collides with a utility pole and is brought
to rest in 0.30 s. Find the magnitude of the
force exerted on the car during the collision.
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To increase the momentum of an object, one should
apply a large force for a long period of time.
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Decreasing momentum also requires an impulse.
?mv Ft
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A great ?mv can be accomplished with little force
(F) if the force is applied over a large time
(t).
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If you lost control of your car, would you rather
run into a brick wall or a stack of hay?
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Other examples of extended t a padded
dashboard, airbags, bent-knee landings, mats
for gymnasts, a glass dish dropped on a
carpeted floor.
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When the time of impact is extended, it reduces
the force of impact.
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Why is hail more damaging than rain?
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Bouncing objects require a greater force to
change their momentum than an object that doesnt
bounce.
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The change in momentum is greater when an object
bounces, therefore a greater impulse is needed.
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To change the momentum of an object, an outside
unbalanced force must be applied.
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Internal forces are always in balanced pairs and
have no effect on the total momentum of the
system.
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If no net force or impulse acts on a system,
the momentum of that system cannot change.
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This is the law of conservation of momentum In
the absence of an external force, the momentum
of a system remains unchanged.
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A 76 kg boater is at rest in his 45 kg boat. If
he steps out of the boat at a velocity of 2.5 m/s
to the right, what is the final velocity of the
boat?
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Newtons Second Law states that if no net force
is exerted on a system, no acceleration occurs.
Does it follow that no change in momentum occurs?
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Newtons Third Law states that the force a cannon
exerts on a cannonball is equal and opposite to
the force the cannonball exerts on the cannon.
Does it follow that the impulse the cannon exerts
on the cannonball is equal and opposite to the
impulse the cannonball exerts on the cannon?
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The forces involved in impulse are not constant.
The force starts small, increases to a maximum,
then decreases. In calculations we use the
average force.
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