What are the three stages of matter and how?

How many molecules are present in 3 mols of silicon dioxide (sio2)?

Positrons are spontaneously emitted from the nuclei of

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.