30 multiple-choice questions covering all 4 topics of Unit 4 — momentum, impulse, conservation, and collisions. Use g = 10 m/s².
Always start with conservation of momentum. If no external force acts on your system, total momentum before = total momentum after. This single equation solves most Unit 4 problems.
Watch your signs — momentum is a vector. Pick a positive direction and stick with it. Object moving left = negative momentum.
Check if KE is conserved. Elastic? Yes, both p and KE conserved. Inelastic? Only p conserved — KE is lost to heat, sound, or deformation.
Use impulse-momentum when forces vary over time. Impulse = area under F-t graph = Δp. This is your friend when force isn't constant.