Use the formula: change in momentum = final momentum – initial momentum
Write momentum as p = mv
Calculate initial momentum: p_i = m v_i
Calculate final momentum: p_f = m v_f
Subtract initial momentum from final momentum: Δp = p_f – p_i
For constant mass: Δp = m(v_f – v_i)
If mass changes, use: Δp = m_f v_f – m_i v_i
Keep direction in mind, since momentum is a vector
Use consistent units: kg for mass and m/s for velocity
Momentum units are kg·m/s
Change in momentum has the same units as momentum