College Board-Aligned Original Notes

AP Physics 1: Algebra-Based Unit 3 Topic 4: Conservation of energy

Energy conservation tracks transfers and transformations so total energy of an isolated system remains constant.

Unit 3: Work, Energy, and Power. College Board exam weighting listed for this unit: 18%-23% of multiple-choice exam score.

What to Know

Mechanical energy is conserved when only conservative forces do work within the system.
External work changes the total energy of a chosen system.
Friction can transform mechanical energy into thermal energy while total energy is still conserved.
Always connect this topic back to the larger unit: Work, Energy, and Power.

Detailed Notes

Conservation of energy belongs to Unit 3: Work, Energy, and Power. Energy conservation tracks transfers and transformations so total energy of an isolated system remains constant. Start by naming the system, choosing axes or a sign convention when needed, and identifying which physical quantity is changing.

Key relationships: Mechanical energy is conserved when only conservative forces do work within the system. External work changes the total energy of a chosen system. Friction can transform mechanical energy into thermal energy while total energy is still conserved.

Model to use: Use bar charts to show kinetic, potential, and thermal energy before and after an event. A strong model should include labels, directions, units, and the reason each relationship applies.

AP-style move: Choose the system carefully because that choice decides whether energy crosses the boundary as work. For free-response work, write the principle first, show the setup, and then interpret the result in the physical context.

Key Vocabulary

Mechanical energy

The sum of kinetic and potential energies in a system.

Energy bar chart

A representation showing how energy is stored before and after an interaction.

Isolated system

A system with no net energy transfer across its boundary.

External work

Energy transferred into or out of a system by an outside force.

Thermal energy

Internal energy associated with microscopic motion and temperature.

Quick Practice

How would you explain Conservation of energy in one or two AP-style sentences?

Name the concept, apply it to a specific example or source, and explain the reasoning that connects the evidence to your answer.

Official Alignment

Reference and Attribution

AP Physics 1 concept reference: AP Physics 1: Concise Summary Notes by IITian Academy. EduCompanion used this source as a topic checklist and conceptual reference, then rewrote the study notes in original wording.

AP Physics 1: Concise Summary Notes