To solve the exercise it is necessary to apply the concepts related to kinetic energy by rotation and the moment of rotational inertia.
Rotational energy is defined as

Where,
I = Inertia moment
Angular velocity
While the Rotational inertia of each blade is given as

Where,
m= mass
l = length
We have also that the assembly of the motor has three blade, then the total rotational inertia is


Replacing with our values


We have the angular velocity in rev per minute then in rad per second is


Then the total Kinetic Energy at the system is


Therefore the total Kinetic Energy at the system is
