Question

In the formula b=D\(\sqrt{\frac{3P_w}{\sigma_t}}\), what is the unit of Pw?

(a) N/mm^2

(b) N/m

(c) KN/mm

(d) N/m^2

This question was addressed to me in an online quiz.

This intriguing question originated from IC Engine in portion Design of IC Engine Components of Automotive Engine Design

Answer 1

Right option is (a) N/mm^2

To explain I would say: Pw is the allowable radial wall pressure on the cylinder wall and pressure is defined as a force upon the unit area. Hence, N/mm^2 is the unit.