Key Concepts: Linear Momentum

Momentum

• Linear momentum is the product of mass and velocity: p = mv.
• SI unit: kg·m/s. Momentum is a vector in the same direction as velocity.
• A heavy slow object and a light fast object can have the same momentum.

Newton's Second Law (Momentum Form)

• F = dp/dt — Force equals the rate of change of momentum.
• For constant mass: F = m(dv/dt) = ma (the familiar form).

Conservation of Momentum

• In an isolated system (no external forces), total momentum before = total momentum after any interaction.
• This applies to collisions, explosions, and any internal interaction.