Problem defining a power measurement on Creo Parametric

Hi all 

I'd like to set a power measurement on Creo by taking into account a strength that I have previously defined.
For the time being, the power defined without taking into account this frictional forces is defined as a Torque* (Rotational Speed). 
I've tried to define power as a force*speed, but speed doesn't change depending on how much force I'm applying to it.

Thank you in advance for your help!