The difference between the carbon 12 and carbon 14 isotopes is the
atomic numbers
number of protons
number of neutrons.
number of electrons.

What happens to light waves from a star as the star moves away from earth?

There are two-speed cameras, one in an are where the speed limit is 30 km/h and another where the speed limit is 50 km/h. in which will there be a smaller time interval between the photographs? explain your answer.

The average density of the planet uranus is 1.27 103 kg/m3. the ratio of the mass of neptune to that of uranus is 1.19. the ratio of the radius of neptune to that of uranus is 0.969. find the average density of neptune.