# Impulse $\vec J$

The “hardness” of an impact/collision.

$$\vec J=\vec F\Delta t=\Delta \vec p$$

where $\vec F$ is impact force (constant during the impact), $\Delta \vec p$ total transferred momentum, and $\Delta t$ impact duration. For non-constant impact force, we’ll instead sum up the impulse during all instantaneous moments with an integral: $\vec J=\int \vec F\,\mathrm dt$.

• Vector property
• Symbol: $\vec F$
• SI-unit: Kilogram-metre-per-second $\mathrm{kg\cdot m/s}$