tv/ movies: Born Jul 21, 1952, He starred in this movie: Dead Poets Society - 1989?

Questions

what is the name used to describe materials that can be broken down by nature?

in what substance are eggs rich, which causes silver to tarnish?

what is the speed of a body expressed as a ratio with the speed of sound?

what measure is used for the purity or fineness of gold?

what is the name of the instrument that is used to test the level of charge in a car battery?