2026-08-17 09:21:31: Conservation of Energy

2026-08-17 09:21:32 -04:00
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+[[Work Energy and Power]]
+
+# SUMMARY
+* System of one object can only have KE.
+* Mechanical energy is just KE + PE.
+* If work = 0 and no no conservative forces then ME = 0
+* If work is done then systems total energy changes
+* Choice of system boundary decides if an interaction is internal or external (no shit)
+* Nonconservative forces like friction or air resistance can dissipate mechanical energy as thermal energy or sound.
+
+## Mechanical Energy Components
+* Kinetic energy is energy of movement
+* Potential energy is energy due to position or config
+* Total ME stays the same when only conservative forces act inside the system
+
+By choosing the system carefully, you can set up systems where even if things in the system change no energy exits of enters, called Constant Energy Systems.
+
+When a system energy changes, that change matches the change across the system boundary. Energy entering increases total energy, energy leaving decreases it, and net change equals sum of in and out.
+
+## System Selection and Energy Changes
+
+|Comparison|Falling ball as system|Ball–Earth system|
+|---|---|---|
+|System contents|Ball only|Ball and Earth|
+|Gravity|External interaction; does work on the ball|Internal interaction|
+|Gravitational potential energy|Not included|Included|
+|Energy equation|ΔK=WgravityΔK=Wgravity|Ki+Ug,i=Kf+Ug,fKi+Ug,i=Kf+Ug,f|
+|Mechanical energy conserved when air resistance is negligible?|No; the ball’s kinetic energy changes as energy transfers into the system|Yes; energy converts between kinetic and gravitational potential energy|