if a hydrogen emission line appears at 656.2 nm in the laboratory, what can we say about a cloud of hydrogen gas with this same emission line at 680.2 nm?

Dalton’s model of an atom is the best described as a) a solar system b) a solid sphere c) a cloud d) a scoop of chocolate chip ice cream

Molten iron fills a mould, which has a volume of 200 cm cubed. calculate the volume when the iron cools and solidifies. molten iron has a density of 7.0g/cm cubed. in its solid state, iron has a density of 8.0g/cm cubed.

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.