Based on the law of conservation of energy, how can we reasonably improve a machine’s ability to do work? a. move the machine to a different gravitational field. b. increase the friction between its moving parts. c. reduce the friction between its moving parts. d. redefine the machine’s system boundaries.

Which statement is the best definition of an atom? a) anything that has mass and occupies space. b) the smallest particle that has the properties of an element. c) a substance that cannot be broken down chemically into simpler substances. eliminate d) the smallest unit of a substance that exhibits all of the properties characteristic of that substance.