REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Physics I includes vectors and scalars, one-dimensional motion, plane motion, dynamics of a particle, work and energy, conservation of energy, dynamics of systems of particles, rotational kinematics and dynamics, harmonic motion, sound waves, gravitation, equilibrium of rigid bodies, fluid statics and dynamics, temperature, heat and the first law of thermodynamics, kinetic theory of gases, and entropy and the second law of thermodynamics.