Key Concepts: Conservative vs. Non-Conservative Forces

Conservative Forces

• A force is conservative if the work done is independent of the path — it depends only on start and end positions.
• Examples: gravity, elastic spring force, electrostatic force.
• Work done in a closed loop by a conservative force = 0.
• Associated with potential energy: W = −ΔPE.

Non-Conservative Forces

• Work done depends on the path taken.
• Examples: friction, air resistance, tension (applied by a person), propulsion force.
• Friction always does negative work — it converts mechanical energy to thermal energy.

Energy Conservation with Both

• ΔKE + ΔPE = W_non-conservative.
• If only conservative forces act: ΔKE + ΔPE = 0 (mechanical energy conserved).
• If friction is present: some mechanical energy is lost as heat.