### The 4th edition of this text includes the following major new features:

- An important new classroom-tested approach to the Momentum Principle
- Detailed instruction in computational modeling
- Recurring comparisons between analytical and iterative approaches
- Recurring comparisons between modeling a system as a point particle or as an extended system
- Enhanced discussion of electrostatics and circuits including detailed computed surface charge distributions

### Additional significant improvements

- More homework problems, including more computational problems
- Full coverage of problems in the WebAssign computer homework system
- Clearer indication of problem difficulty
- Answers to odd-numbered problems
- A student solution manual for a selection of the odd-numbered problems
- Updated, extensive instructor resources
- Some lesser-used materials have been removed from the textbook to save weight and cost and are available at no charge on the student web site, matterandinteractions.org/student
- The order of some topics has been changed within chapters, for improved sequencing of concepts

### Other changes:

- Chapter 5: more instruction on multiobject systems; improved analysis of curving motion; dot product introduced to calculate parallel and perpendicular components of the net force, including computationally
- Chapter 6: improved discussion of path independence, including the fact that it is valid only for objects that can be modeled as point particles
- Chapter 7: choice of moving reference frame affects terms in the Energy Principle
- Chapter 8: randomness of emission; lifetime of an excited state
- Chapter 11: more extensive treatment of rotational kinematics, with new homework problems
- What was Chapter 13 on gases has been moved to the
*Matter & Interactions*student site as Supplement S1 - Chapter 14 (effects of electric field on matter): we show in detail the computed distribution of surface charge on a polarized metal block in equilibrium
- Chapter 15 (fields of distributed charges): explicit instruction on Python lists, for sets of source charges and for sets of observation locations
- Chapter 16 (electric potential): instruction on how to calculate potential difference computationally
- Chapter 18 (circuits in terms of charge and field): we show in detail the computed distribution of surface charge on various quasi-DC circuits
- Chapter 20 (magnetic force): corrected analysis of motional emf in the case of a bar moving along rails; updated “Jack and Jill” to “Alice and Bob”
- Chapter 21 (patterns of fields in space): optional section on PN junctions has been moved to the
*Matter & Interactions*student site as Supplement S2 - What was Chapter 25 on waves is available on the
*Matter & Interactions*student site as Supplement S3, with a new section on the wave equation and longitudinal and transverse mechanical waves, with micro and macro analyses

Here is a pdf of a presentation by Ruth Chabay and Bruce Sherwood about the 4th edition.