Physics begins with a study of motion. Objects that move in a straight line at a constant speed are described in this unit. Topics include displacement, speed, velocity and vectors.
In the real world, motion is often changing. Objects that change their velocity -- by speeding up or slowing down or turning -- are the subject of this unit. Topics include acceleration, force and graph analysis techniques.
To explain why objects change their motion, it is necessary to describe the ways that two objects can influence the motions of each other. Topics include force pairs, linear momentum and collisions.
Another way to describe motion or the ability to move is to use the concept of energy -- kinetic, potential and thermal energy. Topics include work, power and energy.
One important special case of accelerated motion or the ability to move is when these phenomena are caused by gravity. Newton came up with a good approximation of the influence of gravitational forces on objects. Topics include inverse-square laws, gravitational forces between any two objects and projectile motion.
Energy concepts can be used to describe atomic or molecular motion as well, which explains some of the macroscopic behaviors of the substance. Topics include elasticity, pressure and buoyancy.