Nvm found the answer and I don't know how to delete question whelp guess I'm stuck with it

Which is not a source of noise pollution? a)airplanes b)acid rain c)machines d)cars

Consider an insulating crystal, made up of layers of atoms. what form would you expect the temperature dependence of the phonon heat capacity to approach at extremely low temperatures if the interlayer coupling is i)very strong (rigid coupling), and ii) very weak. explain.

Your friend increases her force on the desk by 30n . she doesn't change the direction of her push . what happens to the net force on the desk .will the desk accelerate