mechanics, classical

Synonym: Newtonian mechanics. According to classical mechanics, the movements of bodies are regulated by Newton’s three laws of mechanics. The first law states that bodies on which no external force acts stay at rest or move with constant speed along a straight path (“law of inertia”). The second law relates the force acting on a body, the body’s mass and the acceleration caused by the force: Force is equal to mass times acceleration. The third law is the law of “action equals reaction”: If a body A acts on a body B with a certain force, then A itself experiences B acting on it with a force that is equal in strength but has the opposite direction.

An alternative version of the second law uses the concept of momentum: The force acting on a body is equal to the change of that body’s momentum over time.