Work, Energy and Power — Easy Practice (Set 2)

Quick Recap — Energy Conservation & Collisions

• Conservative forces (gravity, spring): work is path-independent and mechanical energy is conserved. Non-conservative forces (friction) dissipate energy as heat.
• Total mechanical energy $= KE + PE$; it stays constant when only conservative forces act.
• Collisions: momentum is conserved in every collision; kinetic energy is conserved only in an elastic collision.
• Coefficient of restitution $e = \dfrac{\text{speed of separation}}{\text{speed of approach}}$: $e = 1$ (elastic), $e = 0$ (perfectly inelastic).
• Power $= Fv$; the commercial unit of energy is the kilowatt-hour (kWh).