Newton’s Laws

Newton's Law

Newton's First Law (Inertia)

An object at rest will stay at rest, and an object in motion will stay in motion unless acted on by a net force.

Mathematically, this is equivalent to saying that if the net force on an object is zero, then the velocity of the object is constant.

$$ \vec{F} = m\frac{d\vec{v}}{dt} = 0 \quad \rightarrow \quad \vec{v} = \text{constant.} $$

Newton's Seond Law

The rate of change of momentum of a body over time is directly proportional to the force applied, and occurs in the same direction as the applied force.

$$ \vec{F} = m\vec{a} $$
  • GRE Physics GR1777: Problem 001

Newton's Thrid Law (Action-reaction law)

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