Engineering Solution

Perhaps you can rephrase your question. A 10 hp motor will deliver 10 hp of mechanical power provided you are operating it at rated speed and voltage as long as it has an efficiency rating of 1.0. All of this information is right on the tag of the motor.

How you convert that rotational energy to mechanical energy is entirely another matter.

Yes you can measure flow and pressure of water and air. You use instruments for this, designed for the task. There are all kinds of formulas depending on what you intend to do. Not too surprising is the fact that conservation of energy works in this area the same as it does for electricity.

for conversion of electrical energy to mechanical

you mean torque ( i.e work done ) so the formula is

torque = hp*frequency (50hz or 60 hz)*5252/rpm

so you get torque in lb-ft

for measurement of pressure air and so on you should use pressure gauge and other related insturements

Your torque formula can't be right for both 50 and 60Hz, and I can't be bothered to calculate which if either, is correct.

But as others have said, you can work out conversion of electrical energy to mechanical power without considering torque.