The maximum power should be developed by the motor at the end of the take-off, and should be equal to N = Fv, where F is the thrust of the propeller — assumed to be constant during the take-off.
The force F is determined from the equations for Newton's second law for the take-off:
F—kP — Pa/g
where P is the weight of the aeroplane and k the coefficient of friction; the acceleration a is v2/25, from which it follows that
and the power is