🧭 Plot Summary
In Unit 4 you counted the energy of motion with KE = ½mv². It’s a powerful tool, but it can’t answer every question. A 0.145 kg baseball at 40 m/s and a 6.0 kg bowling ball at 6.0 m/s carry nearly the same kinetic energy, yet no one would call them equally hard to stop. Something else about motion is at work.
That something is momentum: mass times velocity. Unlike energy, it has a direction, and that single fact is what makes collisions so interesting. In one class you’ll rank real objects by momentum, measure it on a rolling cart, and discover how it scales differently from the energy you already know.
What you will do in this activity
- Rank everyday moving objects by momentum, then see where that ranking disagrees with the kinetic-energy ranking you made in Unit 4.
- Learn that momentum has a direction, and that moving objects can cancel each other’s momentum.
- Measure the momentum of a rolling cart at different speeds and masses.
- Discover the scaling rules: doubling the speed doubles the momentum, where it quadruples the kinetic energy.
- Start thinking about what it takes to stop something with a lot of momentum.
Why it matters
Every question in this unit, from why an egg breaks to how investigators reconstruct a crash, starts with knowing an object’s momentum. This is the foundation for everything that follows.
✅ Self-Check Before You Roll On
Check off each item as you get there. These are not grades — they are your own signal.