🧭 Plot Summary
Collisions look chaotic. Forces spike, things crumple, and everything happens in a few thousandths of a second. But underneath the chaos there’s a rule that always holds: in a system with no net outside force, the total momentum doesn’t change. What one object loses, another gains.
That one rule lets you predict the outcome of a crash without knowing a single thing about the forces. You’ll learn why it’s true, use it on carts that stick together and skaters who push apart, and then measure it yourself on real carts. You’ll also settle an old question: when a semi truck hits a compact car, which one feels the bigger force?
What you will do in this activity
- Learn the law of conservation of momentum and the reason behind it.
- Solve before-and-after problems for objects that stick together and objects that push apart.
- Crash two carts together and measure how well their total momentum was conserved.
- Discover that kinetic energy is not conserved in a collision that sticks, even though momentum is.
- Settle the semi-truck-versus-compact-car question: which one feels the bigger force?
Why it matters
Conservation of momentum is the main tool investigators use to reconstruct crashes. It’s also the check you’ll run on your own collision data in Project 5-2-3.
✅ Self-Check Before You Roll On
Check off each item as you get there. These are not grades — they are your own signal.