There's a car performance site I've been using which calculates various times such as 0 - 60mph etc. when the user submits the weight (kg) and brake horse power (bhp).

I've been trying to work out how they do it, but i've hit a wall. From a further internet trawling i've found a few formulas they might use but i'm still a stuck.

I'm not really a mathematician, more a computer scientist who's interested in how it's done.