The man tries to open the valve by applying the couple forces of F = 75 N to the wheel. Determine the couple moment produced.
Image from: Hibbeler, R. C., S. C. Fan, Kai Beng. Yap, and Peter Schiavone. Statics: Mechanics for Engineers. Singapore: Pearson, 2013.
Solution:
We will assume clockwise moments to be positive. As the person applies the 75 N force onto the wheel, it will create a coupling moment, which we can write as follows:
\circlearrowright^+ M=75(0.15+0.15)
(Note we converted 150 mm to 0.15 m)
M=22.5 N•m \circlearrowright^+
This question can be found in Engineering Mechanics: Statics (SI edition), 13th edition, chapter 4, question 4-73.