Newton's laws

Newton's laws are a set of three laws that describe the behavior of objects when subject to forces.

1. In the absence of external forces, an object at rest will remain at rest. An object in motion will remain in motion with constant velocity.
2. For an object of constant mass over time, its acceleration $\mathbf{a}$ is proportional to the force $\mathbf{F}$ and inversely proportional to its mass $m$.$\mathbf{F}=m\mathbf{a}$If the mass changes over time, a more general statement is$\mathbf{F}=\frac{d\mathbf{p}}{dt}=\frac{d(m\mathbf{v})}{dt}$where the force causes a change of linear momentum in time.
3. If a force is exerted on an object, there is a force of equal magnitude but opposite direction on some other body that interacts with it.