Amore realistic car would cause the wheels to spin in a manner that would result in the ground pushing it forward with a constant force (in contrast to the constant power in part a). if such a sports car went from zero to 28.0 mph in time 1.50 s , how long would it take to go from zero to 56.0 mph ?

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.

conservation of mass

mass before something happens = mass afterwards