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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