The Ca-H line in the spectrum of star is observed to be at a wavelength of [w] nm. For a sample of calcium at rest relative to us, this line is seen at a wavelength of 395.1 nm. What is the radial velocity for this star?

The geological theory that states that pieces of earth's lithosphere are in constant slow motion is the theory of plate tectonics.

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other