If the sport car is moving in a constant force, it also means constant acceleration. Regardless of friction, the constant power of the engine of the sport car implies that the kinetic energy of the car increases linearly with time. Therefore, if the car went from zero to 28.0 mph in time of 1.50 seconds, then the speed of the car will increase to 3 seconds if it will go from zero to 56.0 mph.