Practice question · Multiple choice
A block sliding to a halt by friction seems to destroy energy. Why is energy still conserved?
Hints
- Touch a surface after something has slid across it.
- Conservation says energy changes form, not that it disappears.
Show the answer
D. Into thermal energy of the block and surface
Why
Friction converts organised kinetic energy into random molecular motion. Nothing is lost; what changes is the form, and that one-way conversion is where the second law enters.
Practise Conservation of Energy
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