Q: why does a sheet of sandpaper become warm when you rub it against a wooden board?
possible answers: a. heat in the air is transferred to the sandpaper, b. matter in the sandpaper is converted into heat, c. the chemical energy in the wood is converted to thermal energy, d. the mechanical energy of the moving sandpaper is converted to thermal energy

If we relied solely on the nonrenewable resources found in the u. s., which one would we run out of first at current usage levels? a. natural gas b. oil c. uranium d. coal

Which of the following are used in an electrochemical cell? a. electrodes b. electrolyte c. terminals d. all of the above

Students in an introductory physics lab are performing an experiment with a parallel-plate capacitor made of two circular aluminum plates, each 11 cm in diameter, separated by 1.0 cm. how much charge can be added to each of the plates before a spark jumps between the two plates? for such flat electrodes, assume that value of 3×106n/c of the field causes a spark.