Nothing is free
Can a machine give out more work than it takes in?
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Step 1 of 4
- A machine run takes in 4000 J of work.
- Of that, 3400 J comes out as useful work.
- The missing 600 J is heat in the moving parts.
- Output plus heat always equals input.
Rule
No. A machine cannot give out more work than it takes in. Friction turns some of the work into heat.
People have designed machines meant to run for ever. None works. Friction and air resistance turn some of the energy into heat. So less work comes out than goes in.
A machine takes in 4000 J. It gives out 3400 J. The other 4000 − 3400 = 600 J became heat.