AI Tutor
Imagine standing on an ice rink with two objects sliding toward you: a 0.145Β kg0.145\text{ kg} baseball flying at 40Β m/s40\text{ m/s} (about 90Β mph90\text{ mph}), and a 6Β kg6\text{ kg} bowling ball slowly rolling at 1Β m/s1\text{ m/s}.
Both are equally difficult to stop, but for completely different reasons: one packs intense speed, while the other packs massive inertia.
How do physicists combine mass and velocity into a single, exact measurement of motion?

The Momentum Equation

In the 1630s, RenΓ© Descartes introduced the idea of a 'quantity of motion,' which Isaac Newton later formalized in his Principia as linear momentum.
Linear momentum (symbol p⃗\vec{p}) is the product of an object's mass mm and its velocity v⃗\vec{v}:
p⃗=mv⃗\vec{p} = m\vec{v}
Since mass is measured in kilograms (kg\text{kg}) and velocity in meters per second (m/s\text{m/s}), the standard SI unit for momentum is kgβ‹…m/s\mathbf{kg\cdot m/s}.
What happens if two identical cars travel at the exact same speed, but in completely opposite directions?

Momentum is a Vector

A vector is a quantity that has both a numerical magnitude and a specific direction in space.