Momentum

Momentum is mass in motion, and is represented by the variable $p$ with the unit $\frac{\text{kg} \times \text{m}}{\text{s}}$¹⁾. Each property of momentum is transcribed from each one of Newton's Laws of Motion.

Recall that the first law is the law of inertia and is in effect when $F_{net} = 0$. In these situations where momentum is constant, it is equal to mass times velocity.

• $p = mv$ where $p$ is momentum, $m$ is mass²⁾, and $v$ is velocity³⁾.

The second law of motion deals with changing velocities, or where $F_{net} \ne 0$, and as such momentum here is represented as a change. Change in momentum is also equal to force times time elapsed, which is derived from the force equation $F = ma$.

• $\Delta p = m\Delta v$ where $\Delta p$ is the change in momentum, $m$ is still mass, and $\Delta v$ is the change in velocity.
• $\Delta p = Ft$ where $\Delta p$ is change in momentum, $F$ is force⁴⁾, and $t$ is time⁵⁾.

The third law states that for every force there is an equal and opposite force. This applies to momentum aswell, however instead of forces it is momentum impulses that hold an equal and opposite reaction.

• $\Delta p = -\Delta p$, in other words, whatever momentum one object loses the other one gains.