1) The mass of an electron is 9.11\times 10^{-31}~\rm kg. If the de Broglie wavelength for an electron in a hydrogen atom is 3.31\times 10^{-10}~\rm m, how fast is the electron moving relative to the speed of light? The speed of light is 3.00\times10^8 ~\rm m/s.
2) The mass of a golf ball is 45.9g . If it leaves the tee with a speed of 75.0m/s , what is its corresponding wavelength?