A volcano ejects a glowing chunk of lava straight up.
It travels 6.0 seconds before it stops and begins to fall back to earth.
Calculate the speed the lava had leaving the volcano.

Remember that rust prevented by placing a sacrificial electrode in electrical contact with the iron. the sacrificial electrode must be composed of a metal that  oxidizes  more easily than iron (that is, it must be below iron in table 18.1).