The secondary unbalanced force produced by the reciprocating parts of a certain cylinder of a given engine with crank radius r and connecting rod length l can be considered as equal to primary unbalanced force produced by the same weight having

• A. an equivalent crank radius r2/4l and rotating at twice the speed of the engine
• B. r2/4l as equivalent crank radius and rotating at engine speed
• C. equivalent crank length of r2/4l and rotating at engine speed
• D. none of the mentioned