I am trying to relate two concepts, Power and Kinetic Energy, using a small DC motor. Given the no-load max angular velocity w (rads/s) of the motor and the current drawn (A) at a given voltage (V) the power being used (P) in Watts is: P = V x A Given the no-load max angular velocity w (rads/s) and assuming the armature is a cylinder of uniform density, known radius (r) and known mass (m) the kinetic energy (Joules) of the armature is given by KE = 1/2 I w^2 Where I is the moment of intertia given by I = 1/2 m r^2. So I have the Watts (P) being "consumed" and KE in Joules. Can I use this to calculate the efficiency of conversion from electrical to mechanical (under the stated conditions)? Can I simply express that in 1 second the efficiency is KE / P x 100? Basically, I am having trouble reconciling the time dimension of Power (J/s) Thanks in advance.