Differences differences between gravity and acceleration due to gravity

"why is graphite used instead of gold or copper wires to conduct electricity in very hot situations such as an industrial kiln? " that's the question, but the thing is, i don't even understand what an "industrial kiln" xd assistance would be < 3

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

How do we measure or think of speed in the united states?