Why does a black car gets hotter in the sun than a white car in the sun?

That has to do with how colour is seen. What happens is black absorbs all light (theoretically, in reality some light is reflected otherwise we wouldn't see it), which shows our eyes nothing. White reflects all light, which shows our eyes white. Black, absorbing all light, stores a massive amount of heat as radiation (no not like Radioactive Waste radiation), which is then radiated out. Basically, black gets hot faster because it absorbs more light.