Momentum (and related stuff)

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Momentum (and related stuff)

• Kellee Nicholas
• Kevin Kev Williams
• Dave Garbe

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IMPULSE AND MOMENTUM

• Momentum-The product of the mass of a moving
  particle multiplied by its linear velocityMSN
  online
• -P(momentum)m(mass)v(velocity)
• Impulse- A force applied over a period of
  time.
• -F(force)?t(change in time)

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IMPULSE AND MOMENTUM(CONTINUED)

• All moving objects have momentum.
• Momentum is conserved when no outside forces act
  on a system (sparknotes.com)

• mvf - mvi -- change in velocity caused by an
  impulse
• Examples
• Air bags in automobiles
• Padded dashboards
• Egg thrown into sheet

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INELASTIC COLLISIONS

• Inelastic collision a collision in which the
  kinetic energy of the system is not conserved
• Kinetic energy of the colliding objects is
  transformed into other non-mechanical energy
• heat energy
• sound energy

• In an inelastic collision, the two colliding
  objects stick together and move with the same
  post-collision speed.
• Examples
• Two billiard balls
• Golf club and ball
• Hammer and nail head
• Two coupled railroad cars
• Falling object and ground

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SAMPLE PROBLEM 1(INELASTIC COLLISIONS)

• A 15-kg medicine ball is thrown at a velocity of
  20 km/hr to a 60-kg person who is at rest on ice.
  The person catches the ball and subsequently
  slides with the ball across the ice. Determine
  the velocity of the person and the ball after the
  collision.

• BEFORE
• PERSON
• m 60 kg
• v 0 km/hr
• MEDICINE BALL
• m 15 kg
• v 20 km/hr
• AFTER
• PERSON
• m 60 kg
• v ? km/hr
• MEDICINE BALL
• m 15 kg
• v ?

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SAMPLE PROBLEM 1(CONTINUED)
BEFORE AFTER
PERSON (60)(0) 0 60v
BALL (15)(20) 300 15v
TOTAL 300 300
60v 15v 300 75v 300 v 4 km/hr Since
momentum is conserved, the total momentum after
the collision is equal to the total momentum
before the collision.
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ELASTIC COLLISIONS

• Colliding objects bounce perfectly in perfect
  elastic collisions
• Example
• A moving billiard ball collides head-on with a
  ball at rest and causes the second ball to move
  away with a velocity equal to the initial
  velocity of the first ball

• Elastic Collision when objects collide without
  being permanently deformed and without generating
  heat
• Sum of momentum vectors are the same before and
  after each collision

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SAMPLE PROBLEM (ELASTIC COLLISION)

• BEFORE
• TRUCK
• m 3000 kg
• v 10 m/s
• CAR
• m 1000 kg
• v 0 m/s
• AFTER
• TRUCK
• m 3000 kg
• v ? m/s
• CAR
• m 1000
• v 15 m/s

• A 3000-kg truck moving with a velocity of 10 m/s
  hits a 1000-kg parked car. The impact causes the
  1000-kg car to be set in motion at 15 m/s.
  Assuming that momentum is conserved during the
  collision, determine the velocity of the truck
  after the collision if the car moves off at 15
  m/s.

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SAMPLE PROBLEM WITH WORK(ELASTIC COLLISIONS)
BEFORE AFTER
VAN (3000)(10)30000 3000v
CAR 0 (1000)(15)15000
TOTAL 30000 30000
3000v 15000 30000 3000v 15000 v 5 m/s
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QUIZ QUESTION 1

• Granny (m80 kg) whizzes around the rink with a
  velocity of 6 m/s. She suddenly collides with
  Ambrose (m40 kg) who is at rest directly in her
  path. Rather than knock him over, she picks him
  up and continues in motion without braking.
  Determine the velocity of Granny and Ambrose.

• BEFORE
• GRANNY
• m 80 kg
• v 6 m./s
• AMBROSE
• m 40 kg
• v 0 m/s
• AFTER
• GRANNY
• m 80 kg
• v ? m/s
• AMBROSE
• m 40 kg
• v ? m/s

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QUIZ QUESTION 1(ANSWER)
BEFORE AFTER
GRANNY (80)(6)480 80v
AMBROSE (40)(0)0 40v
TOTAL 4800480 80v40v480
80v 40v 480 120v 480 v 4 m/s The total
momentum before the collision (possessed solely
by Granny) equals the total momentum after the
collision (shared by Granny and Ambrose).
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QUIZ QUESTION 2

• CAR A 500 kg 30 m/s
• CAR B 600 kg 20 m/s
• The two cars stick together and continue in
  motion
• A. What type of collision is this?
• B. What is the final speed of the two cars?

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ANSWER (QUIZ QUESTION 2)

• A Inelastic Collision
• B m1v1 m2v2 mnvn
• 500(30) 600(20) (500 600)v
• 15000 12000 1100v
• v 24.5454 m/s

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QUIZ QUESTION 3

• BEFORE
• HAMMER
• M 2.5 kg
• V 6 m/s
• NAIL
• M .16 kg
• V 0 m/s
• AFTER
• HAMMER
• M 2.5 kg
• V ? m/s
• NAIL
• M .16 kg
• V ? m/s

• Jack is building a new deck in his backyard. He
  is hammering each nail (which is at rest on top
  of each board and has a mass of .16 kg) with a
  hammer moving at 6 m/s and weighing 2.5 kg.
  Since the nail moves with the hammer once it is
  hit, what is the new velocity of the nail and
  hammer?

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ANSWER(QUIZ QUESTION 3)
P mv 2.5v .16v 15 2.66v 15 v 5.64 m/s
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QUIZ QUESTION 4

• BEFORE
• BULLET
• M .035 kg
• V ? m/s
• BLCOK
• M 5 kg
• V 0 m/s
• AFTER
• BULLET
• M .035 kg
• V 8.6 m/s
• BLOCK
• M 5 kg
• V 8.6 m/s

• A 35.0-g bullet strikes a 5.0-kg stationary
  wooden block and embeds itself in the block. The
  block and bullet move together at 8.6 m/s. What
  was the original velocity of the bullet?
  (CAUTION Be careful of the units on velocity.)

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ANSWER(QUIZ QUESTION 4)
0.035v 43.301 v 1237 m/s
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SOURCES

• http//www.physicsclasssroom.com/Class/momentum/U4
  L2d.html
• http//zebu.uoregon.edu/js/glossary/inelastic_col
  lisions.html
• http//www.tpub.com/doephysics/classicalphysics32.
  htm
• Physics Textbook