Momentum & Collisions

Momentum measures the "quantity of motion": $p = mv$ (kg m s⁻¹, a vector).

Conservation of momentum

In any collision or explosion with no external resultant force, total momentum is conserved: $$m_1 u_1 + m_2 u_2 = m_1 v_1 + m_2 v_2$$

Worked example. A $2$ kg trolley at $3$ m s⁻¹ hits a stationary $1$ kg trolley and they stick together. $2(3) + 1(0) = (2 + 1)v \Rightarrow v = 2$