"The total momentum in the universe remains constant." Is this statement true?

What is universal gas constant?

Is the entropy of the universe constant?

The dimension of R (universal gas constant) is-

Show that the total mechanical energy remains constant for a particle executing simple harmonic motion.

Statement : I A charged particle moves perpendicular to a magnetic field. Its kinetic energy remains constant, but momentum changes. Statement II : A magnetic force acts on the charged particle.

Statement I: When a body moves uniformly in a circular its momentum goes on changing but its kinetic energy remains constant. Statement II: vecp =vec(mv), KE =1/2 mv^2 . In circular motion vecv changes, v^2 does not change.

Statement I : Distance between two particles moving with constant velocities always remains constant. Statement II : The relative motion between two particles moving with constant velocities always remains constant.