Chapter 8 Lecture
Chapter 8: Momentum
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Goals for Chapter 8
• Study momentum. • Understand conservation of momentum. • Study momentum changes during collisions. • Add time and study impulse. • Understand center of mass and how forces act
on the c.o.m. • Apply momentum to rocket propulsion.
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Momentum Is a Vector Quantity – Figure 8.1
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Momentum Can Cause Injury (Concussion)
• This is a frame of reference problem just like a passenger in a car. When the brain and skull are moving at the same velocity, there is no problem. If the skull changes abruptly and the brain does not, there is a possibility of an injury.
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Analysis of a Collision – Figure 8.2
• Refer to the worked example on page 223.
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Momentum Is Conserved – Figure 8.3
• Astronauts provide excellent examples of momentum transfer.
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Scoring a "Strike" Is Many Momentum Transfers at Once
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An Astronaut Rescue – Example 8.2
• Refer to the worked example on page 225.
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Rifle Recoil – Example 8.3
• Refer to the worked example on page 226.
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Head-on Collision – Example 8.4
• Refer to the worked example on pages 226 and 227.
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Collision In a Horizontal Plane – Example 8.5 • Refer to the worked example on page 227.
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An Explosion Considered Backward in Time – Figure 8.8 • Refer to the worked example on page 228.
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Particles Don't Separate – Figures 8.9 and 8.10 • Allows us to draw the distinction between elastic
collisions and inelastic collisions.
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Energy in an Inelastic Collision – Figure 8.11 • Refer to the worked example on page 230. Refer to the worked example on page 230.
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We May Do This Experiment – Example 8.6
• Air tracks allow controlled linear collisions.
• Refer to the worked example on page 230.
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The Ballistic Pendulum – Example 8.7
• Often done with a .22 in lab before firearms were forbidden on campus.
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Different Masses – Example 8.8
• Incoming and outgoing velocities are very mass dependent.
• Refer to the worked example on page 232.
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Different Masses – Figure 8.15
• Incoming and outgoing velocities are very mass dependent.
• Refer to the worked example on page 234.
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Billiards? – Figure 8.16
• Different situations depending on the nature of the strike
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A Solved Air Track Problem – Example 8.9
• See the example on page 234.
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Impulse and Duration of the Impact – Figure 8.21 and 8.22 • Again, different situations
depending on the nature of the strike
• Refer to the worked example on pages 237 and 238.
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Everything Acts on the Center of Mass – Figure 8.25 • Refer to the worked example on page 240.
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Rocket Propulsion – Figure 8.27
• Momentum changes themselves are altered as the projectile uses fuel or explodes.
• Refer to Example 8.14.
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