A cylindrical chamber is oriented with its long central axis along the vertical \(y\) axis of an \(x y z\) coordinate system. The top face of the chamber is a piston that can slide up and down to change the chamber volume. The chamber is initially filled with a monatomic ideal gas. When the chamber temperature is lowered, the piston slides downward very slowly at constant velocity until the chamber volume is one-fifth of its original value. At this instant, the contraction stops with the gas in an equilibrium state.

(a) By what factor does the rootmean-square speed of the gas particles change during this contraction? Does this speed increase or decrease?

(b) By what factor does the thermal energy of the gas change during this contraction? Does the energy increase or decrease?