AP Physics 1 · Unit 3 · Topic 3.5
Power
Energy transfers and transformations provide a scalar alternative to tracking every force through motion.
1. Topic Lens
Power is studied through work, energy, and power. Connect the system boundary, interacting parts, and measurable evidence before applying a formula.
2. Why the Formula Works
The relationship is built from definitions and conservation reasoning:
- For a small displacement, work is the force component along motion times displacement.
- Newton's second law and vdv=a dx convert the accumulated work into an integral of mv dv.
- Evaluating the integral yields the change in ½mv².
3. Detailed Visual Model
4. Worked Example and Lab Link
A 2 kg object speeds up from 1 m/s to 3 m/s. Find the net work.
Answer: Wnet=½(2)(3²-1²)=8 J.
Investigation idea: Use a force sensor and motion detector to compare area under F-x with change in kinetic energy.
Common trap: Energy can cross the system boundary; conservation does not mean every named energy stays constant.
Explain how power supports or limits this conclusion: Wnet=½(2)(3²-1²)=8 J.
Official curriculum reference: College Board AP Physics 1 course page. The explanation and worked example are independently written for this study site.