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Chapter 10 Rotational Kinematics and Energy
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Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

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Page 1: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

Chapter 10

Rotational Kinematics and Energy

Page 2: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

Units of Chapter 10• Angular Position, Velocity, and Acceleration

• Rotational Kinematics

• Connections Between Linear and Rotational Quantities

•Rolling Motion

• Rotational Kinetic Energy and the Moment of Inertia

• Conservation of Energy (Not required)

Page 3: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-1 Angular Position, Velocity, and Acceleration

Page 4: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-1 Angular Position, Velocity, and Acceleration

Degrees and revolutions:

Page 5: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-1 Angular Position, Velocity, and Acceleration

Arc length s, measured in radians:

Page 6: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-1 Angular Position, Velocity, and Acceleration

Page 7: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-1 Angular Position, Velocity, and Acceleration

Page 8: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-1 Angular Position, Velocity, and Acceleration

Page 9: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-1 Angular Position, Velocity, and Acceleration

Page 10: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-2 Rotational Kinematics

If the angular acceleration is constant:

Page 11: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-2 Rotational Kinematics

Analogies between linear and rotational kinematics:

Page 12: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-3 Connections Between Linear and Rotational Quantities

Page 13: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-3 Connections Between Linear and Rotational Quantities

Page 14: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-3 Connections Between Linear and Rotational Quantities

Page 15: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-3 Connections Between Linear and Rotational Quantities

This merry-go-round has both tangential and centripetal acceleration.

Page 16: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-4 Rolling MotionIf a round object rolls without slipping, there is a fixed relationship between the translational and rotational speeds:

Page 17: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-4 Rolling MotionWe may also consider rolling motion to be a combination of pure rotational and pure translational motion:

Page 18: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-5 Rotational Kinetic Energy and the Moment of Inertia

For this mass,

Page 19: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-5 Rotational Kinetic Energy and the Moment of Inertia

We can also write the kinetic energy as

Where I, the moment of inertia, is given by

Use this equation to calculate I, for a few point masses.

Page 20: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-5 Rotational Kinetic Energy and the Moment of Inertia

Moments of inertia of various regular shapes can be calculated using these known results:

Page 21: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

Summary of Chapter 10• Describing rotational motion requires analogs to position, velocity, and acceleration

• Average and instantaneous angular velocity:

• Average and instantaneous angular acceleration:

Page 22: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

Summary of Chapter 10

• Period:

• Counterclockwise rotations are positive, clockwise negative

• Linear and angular quantities:

Page 23: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

Summary of Chapter 10

• Linear and angular equations of motion:

Tangential speed:

Centripetal acceleration:

Tangential acceleration:

Page 24: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

Summary of Chapter 10

• Rolling motion:

• Kinetic energy of rotation:

• Moment of inertia for a few points:

• Moment of inertia for different shapes……

• Kinetic energy of an object rolling without slipping:

• Optional: When solving problems involving conservation of energy, both the rotational and linear kinetic energy must be taken into account.

Page 25: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-6 Conservation of Energy

Optional Not RequiredThe total kinetic energy of a rolling object is the sum of its linear and rotational kinetic energies:

The second equation makes it clear that the kinetic energy of a rolling object is a multiple of the kinetic energy of translation.

Page 26: Chapter 10 Rotational Kinematics and Energy - SFSU Physics …wman/phy111hw/lecture notes... ·  · 2011-03-25Chapter 10 Rotational Kinematics and Energy. Units of Chapter 10 ...

10-6 Conservation of EnergyIf these two objects, of the same mass and radius, are released simultaneously, the disk will reach the bottom first – more of its gravitational potential energy becomes translational kinetic energy, and less rotational.