A car is at rest on a horizontal surface. The engine is switched on and suddenly sets the wheels spinning at a constant angular velocity $\Omega$. The wheels have radius $r$ and the coefficient of friction between the ground and the surface of the wheels is $\mu$. Calculate the time $T$ when the wheels start rolling without slipping. If the car is started on an upward slope in a similar manner, explain whether $T$ is increased or decreased relative to the case where the car starts on a horizontal surface.