Two rods of same length and area of cross section and Young's modulii $Y_1$ and $Y_2$ are joined end

Question

Two rods of same length and area of cross section and Young's modulii $Y_1$ and $Y_2$ are joined end to end. The equivalent Young's modulus for the composite rod is

Professor PC Thomas Classes · Answer

For rods in series, equivalent Young's modulus is $\frac{2Y_1Y_2}{Y_1+Y_2}$.