Test the restoring force
Compare spring forces for different displacements from equilibrium.
AP Physics 1 · Unit 3 · Work, Energy, and Power
Hooke’s Law and Elastic Potential Energy
Stretch and compress a spring, compare restoring forces, and use elastic potential energy to predict motion.
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Learn by doing
Three ideas you’ll put into motion
Connect displacement and energy
Observe how spring potential energy changes when displacement changes.
Predict a spring-driven motion
Use an energy model to connect a spring’s stored energy with an object’s motion.
The big idea
The key ideas, at a glance.
The force points back
Within the linear spring model, Fs = −kx. The minus sign indicates a restoring force toward equilibrium.
Energy depends on displacement squared
Elastic potential energy is Us = ½kx2. Equal stretch and compression magnitudes store equal energy in the ideal model.
A quick comparison
Double a spring’s displacement magnitude while keeping k fixed.
Force magnitude doublesStored energy quadruples
Teaching this topic?Classroom fit, AP connections, and support
- Classroom fit
- Use for a concept introduction, guided independent practice, or a projected class discussion.
- Before students begin
- Force directions, work, kinetic energy, and conservation of mechanical energy.
- Built-in support
- Prepared scenes, guided prompts, and feedback on lesson questions.
- AP Physics 1 connections
- Unit 3: elastic potential energy, spring forces, and energy transfer.
- Check for understanding
- Ask why doubling spring displacement does not merely double its stored energy.
- Optional extension
- Investigate the Spring Launch Up a Curved Ramp lab.
Ready to test your thinking?
The first scene is set up. Start the lesson and explore.