**QUESTION**

I cannot figure out why MathCAD 14 is out putting the wrong answer.

I am doing a simple Power calculation using the formula:

P = BMEP * V.s * N/2 where

N = 4400rpm = 73.333rev/s

V.s = 2L = .002m^3

BMEP = 22bar = 2200000Pa

The correct answer is 161.3kW and MathCAD is giving 1014kW.

**REPLIES**

**jhardy1**

I don’t know the formula or its derivation, but 1014 / 161.3 = 6.286 = 2 pi.

It looks like a confusion over appropriate units in the formula - the fundamental unit of cyclic frequency is rad/s = 2 pi x cycles/s. If you enter

```
N = ?
```

into Mathcad, it will return 460.767 1/s (i.e. rad/s), NOT 73.33 rev/s.

**SOURCE**

https://www.eng-tips.com/viewthread.cfm?qid=300879

Above is a snippet.