Mechanical energy that has been lost to friction has actually been destroyed?

Answer 1

Nope. One of the strongest pillars of Physics is the fact that energy is never

destroyed. Energy lost to friction is no longer available to do the job that

you happen to need it for, but it's still there, and it shows up as heat.

Answer 2

No. The energy lost to friction is converted to heat energy in both surfaces, whether or not they are moving.

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false ( apex)