1. Law of inertia
If the net external force is zero, an object at rest remains at rest, and a moving object continues in a straight line with a constant velocity vector.
From force to motion
Why does motion change?
Dynamics studies the relationship between forces and changes in motion. We use Newton’s laws in inertial reference frames.
We use these laws within classical mechanics, in inertial reference frames.
2. Change in momentum
If P denotes the total momentum of a system consisting of a fixed set of particles, the net external force equals the time rate of change of momentum. For one particle, P = m v. If the mass is constant in time, the second law reduces to F_net = m a.
For open systems such as rockets, where mass crosses the system boundary, the momentum flux must also be taken into account; differentiating m(t) v(t) alone is not sufficient.
3. Action–reaction law
The forces two objects exert on each other have equal magnitudes and opposite directions. These forces act on different objects; they do not cancel in the free-body diagram of a single object.
Newton and the history of science
The life of Isaac Newton — University of St Andrews, MacTutor (in English) ↗
Michael Guillen — Five Equations That Changed the World
Popular science reading for those interested in the history of science. The Turkish edition is published by TÜBİTAK; for technical derivations, use the mechanics references below.
Turkish Historical Society library record ↗Spring–mass experiments
Frictionless harmonic oscillator
Equation of motion, a solution determined by the initial conditions, and conversion between kinetic and potential energy.
Open the experimentDamped spring–mass system
Linear viscous friction: three damping regimes, an analytical solution and mechanical energy loss.
Open the experiment