What happens if two motors are connected in series?

If one motor shuts down due to mechanical failure or if it is turned off, the other will continue running as the circuit is not broken.

IN SERIES, if one of the motors breaks down, the circuit will be broken and neither motor will run. IN PARALLEL, if one motor shuts down due to mechanical failure or if it is turned off, the other will continue running as the circuit is not broken. The only consequence of having two motor in series is it will run faster than the other as the power will not be evenly distributed between both motors because the internal resistances will differ as a result of living in an imperfect world.