A long rod of uniform rectangular section with thickness t, originally straight, is bent into the form of a circular arch with displacement d at the mid-point of span l. The displacement d may be regarded as small as compared to the length l. The longitudinal surface strain is

A long rod of uniform rectangular section with thickness t, originally

1.	A long rod of uniform rectangular section with thickness t, originally straight, is bent into the form of a circular arch with displacement d at the mid-point of span l. The displacement d may be regarded as small as compared to the length l. The longitudinal surface strain is
A.	\(\frac{{2td}}{{{l^2}}}\)
B.	\(\frac{{4td}}{{{l^2}}}\)
C.	\(\frac{{8td}}{{{l^2}}}\)
D.	\(\frac{{16td}}{{{l^2}}}\)
Answer» C. \(\frac{{8td}}{{{l^2}}}\)