🧭 Plot Summary
In Activity 4-1-1 you learned that work changes an object’s motion, and that the energy it gains or loses shows up as kinetic energy. Now you’ll pin that energy down with a number. Kinetic energy depends on two things, mass and speed, but not equally. One of them gets squared.
You’ll start by guessing which moving objects carry the most energy, then calculate and find out how wrong your gut was. Then you’ll test the rule in the lab by rolling a cart down a ramp, changing its speed first and its mass second, and watching what the numbers do.
What you will do in this activity
- Predict which everyday moving objects carry the most energy, then calculate and find out.
- Roll a cart down a ramp from three different heights and measure how its speed and KE change.
- Add mass to the cart and see whether KE follows the mass or the speed.
- Discover the doubling rules: ×2 mass gives ×2 KE, ×2 speed gives ×4 KE.
- Connect KE back to work: net work changes KE, which is why fast things take so long to stop.
Why it matters
Every energy question in this unit needs a way to count energy of motion: how fast a pendulum swings at the bottom, how fast a rider leaves a slide, how far a car skids. This is the formula you’ll use for all of them.
✅ Self-Check Before You Roll On
Check off each item as you get there. These are not grades — they are your own signal.