Momentum · 01 / 04

Momentum

Momentum combines mass with velocity, so it carries both an amount and a direction. Reversing velocity reverses momentum.

The learner question

What information does momentum keep that kinetic energy throws away?

Momentum uses velocity, not speed. Two objects can have the same kinetic energy while carrying momentum in opposite directions.

Core relationship

\vec p = m\vec v

Mass is scalar. Velocity supplies the direction.

Vector lab

mass

3.0 kg

velocity

4.0 m/s

momentum

12.0 kg·m/s

Mass3.0 kg

Velocity4.0 m/s

Momentum

12.0 kg·m/s

Changes sign when velocity reverses.

Kinetic energy

24.0 J

Uses $v^2$ , so reversing direction leaves the value unchanged.

Same momentum, different motion

A larger mass can carry the same momentum at a smaller speed. Momentum alone does not determine kinetic energy.

Transfer check