Kinematics Graphs

Graphs can tell the story of an object's motion. On a position-time graph, the slope is velocity. On a velocity-time graph, the slope is acceleration and the area under the line is displacement.

Momentum and Impulse

Momentum is a measure of an object's 'unstoppability'. Impulse is the force applied over a period of time that causes a change in momentum. To change an object's momentum, you must apply an impulse.

Formula: p = mv and J = FΔt = Δp

Conservation of Momentum

In any collision where there are no external forces, the total momentum of all objects before the collision is equal to the total momentum of all objects after the collision. Momentum is transferred, not lost.

Formula: Σp_initial = Σp_final

How Car Safety Features Work

Airbags and crumple zones save lives by manipulating the Impulse-Momentum theorem. They are designed to increase the time of the collision (a bigger Δt). Because the change in momentum (Δp) is the same, increasing the time dramatically reduces the force (F) on the occupants to survivable levels.