Mach number is a ratio of the speed of a body (aircraft) to the speed of sound in the undisturbed medium through which the body is traveling. It is said that the aircraft is flying at Mach 1 if its...
If we consider the atmosphere on a standard day at sea level static conditions, the speed of sound is about 761 mph, or 1100 feet/second.
source: http://www.grc.nasa.gov/WWW/K-12/airplane/sound.html
depends completely on the cars aerodynamic setup, gear ratios, ect. The highest recorded speed however of an F1 car was by the 2005 Honda F1 car which reached a flash reading of 400km/h at Bonneville...